We prospectively evaluated 75 patients, 30-77 years old, with severe phimosis. All patients were treated surgically by complete circumcision and all surgical specimens were sent for histological evaluation. All patients with histologically proven lichen sclerosus et atrophicus (LSA) (eight patients, 10.6%) were re-evaluated 6 months postoperatively, and all but one were examined 5 years after the operation. All patients with histologically proven balanoposthitis (BP) (47 patients, 62.6%) were also re-evaluated 6 months postoperatively, and 41 patients 5 years after surgery. This group (BP) was the control group of our study. Six months after the operation, the eight patients with histologically proven LSA all had an excellent convalescence, and the lesions observed during the operation resolved in four patients and regressed in two patients. In one patient the glans presented with a pale grey-white-coloured plaque. Biopsy was performed and a well-differentiated squamous cell carcinoma infiltrating the glans was revealed. The control group of patients with histologically proven BP were also re-evaluated 6 months and 5 years after surgery. An excellent convalescence was observed in all patients who completed the follow-up examination. Care must be taken not to underestimate the potential relationship between LSA and squamous cell carcinoma, because the latter is usually invasive, very aggressive and requires immediate treatment.