When you hear hoofbeats behind you, don't expect to see a zebra.
If you don't recognize this saying or don't understand its meaning, then this web site is not for you.
For those who persist, however, here's an explanation.
Zebra is medical slang. Loosely, zebra means a rare, unusual, or surprising disease or condition.
The word acquired this meaning because of the quotation above, which is frequently used in medical
For reasons I explain in the hard copy version of Zebra Cards, physicians naturally tend to make the
diagnosis of a rare or unusual disease too frequently. For example, although malaria causes fever and
chills, a physician in the United States would be foolish indeed to rank malaria as the most likely cause
of a random patient's fever and chills. This is an extreme example, to be sure, but in less extreme
situations it can be very tempting to leap to the dramatic, unusual diagnosis, particularly in a difficult
It is customary, therefore, to warn physicians-in-training about this tendency, and to do it using the
quotation at the top of this page. The quotation is simply a colorful way of saying that common diseases
are what physicians almost always encounter in practice. (In the United States, the sound of hoofbeats
is most commonly made by horses, not zebras.)
Nevertheless, it is important for physicians to know about rare and unusual conditions. After all, people
have these diseases and they suffer just as much as people with common ills. The hard copy version of
Zebra Cards, therefore, endeavors to teach physicians about unusual medical situations with which
they may someday be confronted, however unlikely the chances.
The hardcopy version of Zebra Cards has an unusual format. It presents, as flash cards bound into a
book, 200 unusual observations a physician might make about an adult patient, along with a scholarly
discussion of the possible ramifications of each observation in North America.