Thirty-six patients who had suffered two or more episodes of erysipelas or cellulitis during the previous year were randomly divided into two equal groups; one group received erythromycin base 250 mg b.i.d. for 18 months, while the other group received no prophylaxis for a similar period. No patients in the treated group developed infection during the 18 months' follow-up but eight of the control group (50%) relapsed and required antibiotic treatment. Prolonged antimicrobial prophylaxis is effective and safe in preventing recurrent episodes of soft-tissue infections.