Thirty-four patients with collagen diseases suffering from onychomycosis were treated with fluconazole and showed remarkable improvement. Thirty-one patients showed improvement while only four patients showed adverse reactions. More than half of the cases with onychomycosis in their fingers showed improvement within four weeks and complete recovery within 20 weeks after the administration of fluconazole. Patients with collagen diseases are liable to have onychomycosis as an opportunistic infection which is recalcitrant and resistant disease from the previous therapy. In this trial it became obvious that fluconazole was not only effective on onychomycosis but also a safe drug for the patients with collagen diseases.