SummaryStudy 1. Eighteen HIV‐positive Caucasian homosexual men with initial positive fungal microscopy were recruited into this prospective, dual‐centre, open‐label study. They received a once‐daily oral dose of 250 mg terbinafine for 12 weeks.Eight were subsequently excluded after screening cultures proved negative. The mean CD4 count of the 10 evaluable subjects was 302/mm3. All 10 positive fungal cultures were confirmed as Trichophyton rubrum.Using an intention‐to‐treat analysis, healthy unaffected nail growth increased from a mean of 1·6mm at baseline to 5·2 mm after 12 weeks’ treatment. Clinical response after treatment was 6·4mm at 36 weeks and 8·0 mm at 48 weeks.Three of the 10 toenail infections were cured mycologically. This 30% cure rate was maintained over 48 weeks’ follow‐up, despite three patients discontinuing the study. One withdrew following a terbinafine‐induced drug rash. Two others stopped treatment during HIV‐related illnesses, but without terbinafine side‐effects.Study 2. Ten HIV‐positive subjects, nine culture‐positive for Candida albicans and one for Candida albicans and Candida glabrata, were recruited into this pilot study. They received 250mg oral terbinafine daily for 14 days. Their average CD4 count was 131/mm3.All patients remained culture‐positive throughout the study. Slight improvements in signs and symptoms were seen in one or two patients but this might well have been attributable to improved oral hygiene. Oral terbinafine at this dosage was therefore not thought an effective treatment for this indication in HIV‐positive patients. The drug was well tolerated and no serious treatment