Including 25 recurrences, the material comprised 87 odontogenic keratocysts (OKCs) from 57 patients, who had been treated in 1974-93. The study included an analysis of clinical and histologic data from the patients' records and from pathologic reports. The men:women ratio was 1.5:1. Most of the patients belonged to the age groups 10-19, 20-29, 40-49, and 60-69 years. Almost 75% of the OKCs were localized in the mandible. The most common site was the angle and ascending ramus area. Recurrences comprised 30.5% of the OKCs. The symphysial area of the mandible had the highest recurrence rate (50%). The diagnosis of Gorlin's syndrome was established in two patients. The recurrence rates for the OKCs that were removed in one or in several pieces were 27.5% and 39%, respectively. In 14/87 (16%) cases, microkeratocysts were histologically found. Parakeratosis was observed in 78/87 (89.5%), ortho- and parakeratosis in 6/87 (7%), and orthokeratosis in 3/87 (3.5%) cases. The recurrence rates were 31.5% and 41% for the OKCs that were removed during 1974, 1984, and 1985-90, respectively. In no case could malignant changes be observed at histologic examination.