Our personal handwashing rules: use hot water and soap, do it after potentially touching something yucky and sing "Happy Birthday" to be sure you're scrubbing long enough. Physicians, though, need to know a lot more. And a small study of third-year medical students in Germany finds that they aren't entirely clear on when handwashing is indicated. The study, published in the American Journal of Infection Control, covered 85 third-year students at Hannover Medical School, most of whom said they'd had at least some clinical experience. Researchers asked the students whether handwashing was indicated in seven situations. Among the students, 21% correctly identified all the true and false indications, while 67% correctly identified the five conditions under which handwashing is appropriate. (That means a third missed at least one.)