The prevalence of onychomycosis is increasing and the primary pathogens may be dermatophytes, nondermatophyte molds, or Candida spp. It may not be satisfactory to treat onychomycosis on the basis of clinical diagnosis alone. Laboratory diagnosis is an important component of the proper management of this fungal infection. Laboratory diagnostic methods for detecting onychomycosis include light microscopy and culture, or histopathology. Management of onychomycosis includes palliation achieved through mechanical debridement of the nail and topical or oral antifungal therapy.