An analysis was made of the clinical features of 312 acceptable cases of odontogenic keratocysts from the files of the Department of Oral Pathology, Indiana University School of Dentistry. A total of 5.1 per cent of the keratocysts were from patients with the basal-cell nevus syndrome and 5.8 per cent were from patients with multiple keratocysts but with no other features of the syndrome. There was a wide age range, with a peak incidence in the second and third decades of life. The mandible: maxilla ratio was 2:1, with the mandibular third molar area and ramus being the most common sites. Dentigerous cyst was the most frequent clinical as well as histologic diagnosis for the majority of the keratocysts in this study. The primordial cyst comprised the greatest percentage of keratocysts (44.4 per cent). A total of 50.3 per cent of the patients were symptomatic before seeking treatment, the most common finding being intraoral drainage and swelling. Their radiographic appearance was quite variable, although they frequently resembled ameloblastoma. These cysts may be very aggressive clinically. They have a relatively high recurrence rate, as previously reported in the literature, in comparison with other types of odontogenic cyst. The findings in this study support the theory that the histologic appearance of an odontogenic keratocyst may be assumed by any of the odontogenic or nonodontogenic cysts.