Adverse cutaneous reactions to drugs are among the most frequent adver
se reactions to many systemically administered therapeutic agents. In
addition to these reactions resulting in discontinuation of drugs impo
rtant to a patient's treatment, some adverse cutaneous reactions to dr
ugs may result in substantial morbidity or even death. The early recog
nition of these clinically important reactions is made on clinical gro
unds. Epidemiologic data do suggest however, that a relatively small n
umber of drugs are responsible most often for these most serious react
ions.