During 1966-75 the Swedish Adverse Drug Reaction Committee received some 300 reports of reactions to methyldopa. As the Swedish rules for reporting adverse reactions emphasize the importance of severe and unexpected reactions, the relative incidence of various adverse effects differs greatly from what would be found in an intensive study. The three most commonly reported reactions are fever, hemolysis and hepatic effects. Two-thirds of these patients were women. The median age of the groups differed, from 57 years (hepatic effects) to 69 years (hemolysis). The clinical picture of the different reactions was consistent, in the main, with what has been described previously. Between 70 and 85% of the patients in these groups were admitted to hospital because of the adverse reaction.