Drug-induced fever is a frequent (3-5% of all adverse effects) but under recognized adverse effect of several drugs. Hydroxyurea, an antimetabolite cytostatic agent, has rarely been involved in the occurrence of fever. We report three additional cases of hydroxyurea-induced fever including one case with pulmonary involvement (acute alveolitis). In these cases, the role of hydroxyurea was strongly suggested by the delay to onset of symptoms (16-36 days), the disappearance of fever within a few hours after drug withdrawal, the recurrence of fever shortly after rechallenge in two patients, and the absence of any other obvious cause.