This review deals with tolerance of a new macrolide, roxithromycin from data collected from a number of studies in adults. A total of 2917 adults, 2519 given roxithromycin 150 mg bid, were recruited into 17 multicentre comparative or non-comparative studies. Nine studies were double-blind, against doxycycline, erythromycin estolate (EES), lymecycline or cephradine. Overall the drug was well tolerated: side-effects possibly or probably related to roxithromycin were noted in only 4.1% (120/2917) of all patients, and in 3.1% (15/480) of elderly subjects. The gastrointestinal tolerance of roxithromycin was significantly better than that of doxycycline in four trials, and better than that of erythromycin ethylsuccinate in one study. The incidence of drug-related liver function test abnormalities following roxithromycin therapy was low and compared favourably with data published on erythromycin. Roxithromycin shows a satisfactory safety profile at the recommended daily dosage of 150 mg bid in adults.