Hillary Clinton’s dizzy spell on Sunday, followed by the revelation she has pneumonia, along with Trump’s highly unusual and terse medical disclosure, have made this a central issue in the 2016 election.

When Arizona’s Senator John McCain was the Republican presidential nominee, McCain, then 71, famously allowed reporters to pore through thousands of pages of his medical records to quash any concerns about his previous battles with melanoma.

In contrast, Trump released a one-page note that has been roundly criticized for its lack of specifics and general bombast. His New York doctor, Harold Bornstein, claimed that Trump would be “the healthiest individual ever elected to the presidency” and that his lab test results were “astonishingly excellent.” The 2015 letter also said Trump had “only positive results” from his various medical tests—which is considered “nonsense” phrasing among clinicians, as the Atlantic notes.

Clinton’s two-page physician’s letter revealed about the same level of medical history and blood test results as Barack Obama and Mitt Romney had released during their White House bids. But Obama’s former physician argues that both Trump and Clinton must be held to a higher standard considering their ages. At 70, Trump would be the oldest first-term president ever elected if he were to win in November; Hillary Clinton wouldn’t be far behind—she’ll turn 69 towards the end of October. (Ronald Reagan, who previously held the record, was just a few months shy of 70 when first elected.)

“Having been in practice for 50 years serving a predominantly geriatric patient population, and now a septuagenarian myself, I can attest that the American people need much more medical information from these candidates,” Dr. David L. Scheiner wrote in a Washington Post op-ed in late August.

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Now, the Clinton campaign has promised to release more extensive information about her health and medical records to put any concerns to rest.

Trump says he has had a new physical exam and will be releasing more information; on Wednesday he’s also set to have an hour-long interview with television personality Dr. Mehmet Oz about his “personal health regimen,” which will air Thursday. But Dr. Oz has also said that it’s up to Trump what, if any specifics, he discloses. “I’m not going to ask him questions he doesn’t want to have answered,” Oz said.

With a presidential contest pitting two of the oldest people to ever run for the office, the candidates’ medical fitness—both physical and mental—has become an unusually relevant issue. Fortune has reached out to both campaigns about the matter and will update this post if they respond.

Here are some key questions about Hillary Clinton’s and Donald Trump’s health.

What kind of pneumonia does Clinton have?

In an interview on Monday evening with CNN’s Anderson Cooper, Clinton attempted to address concerns about her health. She said that her physician had recommended five days of rest after her pneumonia diagnosis Friday and that the campaign decided not to disclose the illness then because she “didn’t think it was that big a deal.” She said she would be heading back to the campaign trail within a couple of days. Clinton said that contrary to some reports, she had never actually fainted, and that she felt significantly refreshed once she was in an air-conditioned car and drank some water.

As CNN medical correspondent and physician Sanjay Gupta pointed out after the interview, that still leaves some unanswered questions. For instance, Gupta wondered if a chest x-ray had been performed on Clinton to see how much of her lungs had been affected by the infection. He also explained that there are several different types of pneumonia which can be caused by viral, bacterial, or fungal pathogens.

Since Clinton is reportedly taking antibiotics, it would appear that her brand of pneumonia is bacterial, which is among the most common pneumonia types. And as one physician told the Washington Post in an interview on Tuesday, if caught early, bacterial pneumonia doesn’t require hospitalization and can be successfully treated with antibiotics (all of which appears to be the case with Clinton based on the available information).

Is Clinton up-to-date on her vaccines?

Adults who are over the age of 65 are encouraged to have had two type of anti-pneumonia immunizations—one which protects against 13 strains of pneumococcal bacteria (PCV13) and one which protects against 23 types of pneumococcal bacteria (PPSV23). These vaccinations are recommended because pneumonia disproportionately affects the young and the elderly, whose immune systems tend to be weaker.

It’s not clear whether Clinton has received these vaccinations. Clinton’s immunization records may also be among the information that her campaign releases this week.

It’s worth noting that we don’t know if Trump is up to date on his vaccines or much about his health at all–because he has released even less information than Clinton.

What medications are Trump taking?

Trump’s one-page note only revealed that the GOP nominee takes aspirin daily and is on a low-dose statin for cholesterol. It clearly left out many, many details.

For instance, while it said that Trump has 110/65 blood pressure, it didn’t disclose whether Trump was taking medication for high blood pressure. There is debate within the medical community about what an optimal blood pressure target is, especially for older people like Trump, and how aggressively medications should be used to lower blood pressure to reduce the risk of heart attack and stroke.

Is Clinton receiving the most state-of-the-art medical care?

Clinton’s 2015 doctor’s note disclosed that she takes antihistamines for her allergies; a treatment called Thyroid Armour for hypothyroidism; B12 vitamins; and the anti-clotting drug Coumadin (warfarin) as a precautionary measure, since Clinton has previously had blood clots in her leg and a developed a clot near her brain after her 2012 fall and concussion. (Her physician has insisted that the clot and any adverse effects from the concussion subsided completely within six months of the incident.)

In an interview with KABC-AM last month, Drew Pinsky, a TV personality and internal medicine doctor, said he was “gravely concerned” about the anti-clotting and thyroid drugs prescribed by Clinton’s doctor, which he said are outdated. A new class of drugs with fewer side effect risks, such as Boehringer Ingelheim’s Pradaxa, Bayer AG and Johnson & Johnson’s (JNJ) Xarelto, and Bristol-Myers Squibb (BMY) and Pfizer’s (PFE) Eliquis, have become increasingly popular anticoagulants in recent years.

Still, these new medications come with a risk of dangerous and potentially fatal bleeding episodes. And only one of the three new therapies (Pradaxa) has a Food and Drug Administration (FDA) approved antidote. Some doctors have held off on switching patients to these drugs until there are more widely available bleeding reversal agents on the market—which may happen as soon as this year, Reuters notes.

What other medical tests should Clinton or Trump get?

Scheiner, in his op-ed, recommended that Clinton undergo a new neuro-psych exam to ensure that she has fully recovered from her 2012 fall since the last exam referenced by her doctor occurred in 2013, and the situation may have changed since then.

But he also stressed that Trump needed to release far more detailed medical records and undergo a neuro-psych exam as well, alluding to the mental health concerns that have been (somewhat controversially) raised by a number of psychiatrists and psychologists about the candidate—including whether or not he is a narcissist or sociopath.

“[I]f normal, this would at least put an end to speculation that he has a personality disorder,” said Scheiner, adding “we can ask specific questions about [Clinton’s health] because she has been willing to share some important information, even if it is inadequate. In contrast, we know nothing about Trump’s health.”