Dirithromycin is a new macrolide with a spectrum and degree of in vitro antimicrobial activity similar to that of erythromycin. Compared with erythromycin, dirithromycin has a long elimination half-life enabling once-daily administration, and it also achieves a greater cellular:extracellular concentration ratio and higher concentration in some tissues. Multicentre double-blind clinical trials have shown dirithromycin to be similar in efficacy to erythromycin in the treatment of uncomplicated bacterial infections of the respiratory tract and of skin and soft tissues. Since dirithromycin is at least as well tolerated as erythromycin, with its convenient administration schedule and pharmacokinetic profile it is a useful alternative to erythromycin in the treatment of appropriate community-acquired infections. Definition of the place of dirithromycin relative to that of the other newer macrolides awaits the results of further suitably designed therapeutic trials.