BACKGROUND In tropical primary health care, essential drugs should be safe, effective, and as inexpensive as possible. To treat the very common dermatophyte infections of the skin, one may use inexpensive Whitfield's preparations, more expensive topical imidazole derivatives, or extremely expensive oral antifungals. Because a cream base is felt to be more appropriate than an ointment in tropical conditions, we wanted to compare the effectiveness of Whitfield's cream and a topical imidazole derivative in field conditions in the tropics. METHODS A double-blind trial was performed involving 153 patients with a dermatophyte infection of the skin in Karonga District, Northern Malawi, including 25 patients who were HIV-1-seropositive, comparing Whitfield's cream with clotrimazole cream. RESULTS 75 patients were treated with Whitfield's cream and 78 with clotrimazole cream for a period of 6 weeks. Cure rates ranged from 80% to over 90% depending on the definition of cure. If positive cultures after treatment were used as criterion for treatment failure, six were found in each treatment group. One in each treatment failure group was an HIV-1-seropositive patient. CONCLUSIONS The great majority of patients in the tropics with a dermatophyte infection of the skin can be cured with a topical antimycotic preparation and do not need expensive oral therapy. This also proved to be valid for HIV-1-seropositive patients. Whitfield's cream and clotrimazole cream are both very effective. The lower cost makes Whitfield's cream the treatment of choice in dermatophyte infections of the skin in tropical primary health care.