Twenty-four patients were treated with oral miconazole (250 mg) for a total of 35 episodes of oral candidiasis. Sixteen had various forms of leukaemia and all were massively predisposed to fungal infection because of granulocytopenia and treatment with prednisolone and antibiotics. Clinical cure was observed in all 35 of the treated episodes, with a mean treatment time of five days, cure being observed in two to three days. When patients violating the protocol were excluded, the mycological cure rate was 97%. In 21 episodes there was a recurrence less than one month after miconazole treatment, probably because of reinfection. No side-effects ascribable to miconazole were observed, even in the severely debilitated patients, and the orally administered drug appeared to be superior to other commercially available antimycotic preparations.