Onychomycosis is the most common nail disease caused by dermatophytic fungus, non-dermatophytic molds or yeasts. It is an infection that continues to increase due to various factors such as chronic degenerative diseases. The aim of this study was to evaluate the etiologic diversity of onychomycosis in Mexican patients with chronic-degenerative diseases. The research was performed in 51 adult outpatient of a second level hospital in the city of Puebla, Mexico. Isolation and fungal identification were executed by using conventional methods (Microculture, Auxacolor, CHROMagar-Candida). All patients had onychomycosis on the toenails. Type 2 diabetes mellitus was the most common chronic degenerative disease. According to the richness and abundance of organisms, we found: Candida albicans 17% (9), Candida glabrata 6% (3), Trichophyton mentagrophytes 8% (4), Trichophyton rubrum 4% (2), Trychophyton tonsurans 6% (3), Microsporum canis 6% (3), Scopulariopsis brevicaulis 12% (6), Fusarium solani 19% (10), Penicillium sp. 8% (4) and Aspergillus flavus 14% (7). A high percentage of non-dermatophyte filamentous fungi isolates was obtained indicating the importance of these fungi as causal agents of onychomycosis in this population.