Background. Onychomycosis comprises all fungal infection that affects the nail apparatus. It accounts for up to 50% of nail disorders. This may occur as a primary event or secondary infection of a previously diseased or traumatized nail. The primary pathogens are dermatophytes, non dermatophytes and yeast. Mycological study appears imperative for selection of appropriate treatment. Objective. Studying the mycological pattern of onychomycosis in patients attend Benha University hospital. Methods. The nail clipping and scraping of 45 onychomycosis’ patients were subjected to Potassium hydroxide (KOH) mounts for direct microscopic examination and culture on Sabouraud dextrose agar. Results. Candida spp. were isolated in 46.7% of the samples ( candida albicans was the most common isolates 31.1%). Dermatophytes were isolated in 44.4% of the samples( T.rubrum was the most common dermatophytes 37.8%).. Aspergillus spp (8.9%) was being the only non dermatophytes isolates. The higher percentage of onychomycosis patients were farmers (40%), office workers (28.9%). Toe nail infection was as frequent as finger nail infection (46.7%) each. KOH and culture positivity were 48.9% and 31.1% respectively .Conclusion . Onychomycosis is a common medical problem . T. rubrum and C. albicans were the most prevalent isolates. Proper diagnosis not only allows for more efficient expenditure of funds and services, but also is paramount for the timely alleviation of the condition.