Onychomycosis is considered to be an age related infection. It is a rare disorder in children. This survey was carried out to determine the epidemiological, clinical and causative species of fungal nail infections in children with age less than 16 years old attending our laboratory during five years (2001–2006). Methods We undertook a retrospective study about 2431 children consulting us for suspicion of dermatomycosis. The specimens were examined microscopically and cultured on Sabouraud medium agar. Results Superficial mycoses were mycologically proved in 1390 children. One hundred and twenty-eight (9.2%) of them were onychomycosis, representing 48.5% of 272 cases of nail alterations. Mean age was 11 years. The incidence increased steadily with increasing age. Nail infections were most commonly caused by dermatophytes (57%), toenail was the main location (54.8%). Dermatophytic onyxis were associated with tinea capitis in 37.5% of fingernails cases and tinea pedis in 47.5% of toenails cases. Trichophyton rubrum was the most frequently isolated (65.8%), followed by Trichophyton violaceum (15.1%), Microsporum canis (9.6%) and Trichophyton interdigitale (1.4%). Yeasts were isolated in 41.4% of cases, predominated in fingernails (90.6%). The most important species were Candida albicans (49, 1%), Candida tropicalis (22.7%) and Candida parapsilosis (16.9%). Moulds were isolated in two cases (1.6%). Discussion As in adults, onychomycosis is probably the main nail disease in children. A source of infection should be researched (coexistence of tinea capitis, tinea pedis, dermatomycosis of family members…). It is appropriate to suspect onychomycosis in children to perform mycological diagnosis and undertake early treatment.