Tinea capitis continues to be a common problem in urban pediatric populations. In the United States, the majority of fungal scalp infections are now caused by Trichophyton tonsurans. A significantly smaller percentage of tinea capitis is caused by Microsporum canis. In the past 20 to 30 years, the agents responsible for tinea capitis in this country have been influenced by immigration from Mexico, Puerto Rico, and other Central and South American countries.1 These populations brought T tonsurans with them from locales where it had long been endemic. Prior to the 1950s Microsporum audouinii was responsible for most of the childhood epidemics of tinea capitis in this country. This organism has now virtually disappeared, although the exact factors contributing to this disappearance remain elusive. The fact that certain locales, such as Arizona, were subject to similar migration patterns but remained free of T tonsurans2 makes explaining this change in