Tinea capitis is a disease found throughout the world. It frequently affects children and only rarely adults, usually post-menopausal women. Numerous dermatophytes of the genus Microsporum and Tricophyton can cause tinea capitis and griseofulvin is still today the treatment of choice. To study the effectiveness and tolerability of terbinafine treatment in tinea capitis caused by Microsporum canis we treated 26 patients - 22 children and four women - for a period of 12 weeks. Dosage adopted was 62.5 mg day(-1) in patients weighing less than 20 kg, 125 mg day(-1) in those weighing between 20 and 40 kg, and 250 mg day(-1) in patients weighing more than 40 kg. Clinical and mycological healing was achieved in 22 patients (84.6%), tolerability was excellent and in no cases were side effects or abnormal results in blood chemistry tests observed.