Fifty-eight patients with 119 nodular (2 mm or more in thickness) basal cell carcinomas successfully treated with photodynamic therapy were included in this 1-year follow-up study. The initial cure rate at 3-6 months was 92% after photodynamic therapy, which included an initial debulking procedure and topical application of dimethylsulphoxide in order to enhance penetration of 5-aminolevulinic acid (20% in cream) to which the lesions were exposed for 3 h prior to exposure to light. At examination 12-26 months (mean 17 months) after treatment 113 lesions (95%) were still in complete response. Six lesions (5%) had recurred, located on the face, scalp and ear. The cosmetic outcome was evaluated as excellent to good in 91%. Microscopic examination of biopsies taken from healed areas in 7 patients did not reveal any sign of damage in 5 and only minor alterations in 2.