A 10% aqueous solution of glutaraldehyde was applied to a total of 21 toenails of four patients with onychomycosis. When the nails which were infected on the surface grew out after four to six weeks of therapy, they appeared to be normal and there was no fungal growth on culture. Infection through the entire thickness of the nailplate required four months of topical therapy. Reinfection from the surrounding skin occurred in one patient. Glutaraldehyde applied topically appears promising for the treatment of onychomycosis of the toes.