Four-hundred and ninety-four schoolchildren and 200 children attending a paediatric medical out-patient clinic were screened for clinical evidence of dermatophyte onychomycosis. Only one case was found and mycological investigation showed this to be due to Trichophyton rubrum. The overall prevalence of dermatophyte onychomycosis in the prospective survey of schoolchildren was 0.2%, confirming that this type of infection is very uncommon in children. Seven further cases of nail infection occurring in children under the age of 12 years are reported. These represent all cases collected by our laboratory over a 3-year period. In six cases where culture of nail was positive, the causative organism was T. rubrum. In four cases at least one parent was also found to have dermatophyte onychomycosis; again, T. rubrum was the causative organism in all cases. Dermatophyte onychomycosis in children appears to be of low infectivity, (in contrast to viral wart infection), and a parental source should be suspected and sought.