Photodynamic therapy using 5-aminolevulinic acid (ALA) was administered to our patients. First, a 20% urea ointment (Keratinamin; Kowa Pharmaceuticals, Nagoya, Japan) was generously applied directly to the diseased nail surface and covered with a piece of plastic film wrap for 10 hours. Then, a 20% solution of ALA methyl ester (Sigma-Aldrich Corp, St Louis, Missouri) in aqueous cream (Japanese Pharmacopoeia, Merck Hoei Ltd, Osaka, Japan) was applied to the treated nails, which were sealed with a piece of plastic film wrap and covered with aluminum foil to shut out the light for 5 hours. Before PDT, ALA-induced protoporphyrin IX fluorescence in the nail was confirmed by UV irradiation. The fluorescence was observed at the base of the nail and at the periphery of the onychomycosis lesion. The production of protoporphyrin IX was also confirmed by spectrophotometer. Subsequently, the treatment site, including proximal and lateral nail folds, was irradiated both horizontally and vertically with pulsed laser light at a wavelength of 630 nm at 100 J/cm2 using an excimer-dye laser (Hamamatsu Photonics KK, Hamamatsu, Japan). 5-Aminolevulinic acid PDT was performed once a week. Both patients had a feeling of some pain during irradiation, but it was tolerable and disappeared within a day.