The histology, radiographs, and follow-up information for 142 cases of central giant cell lesions of the jaws were reviewed in an effort to determine which, if any, microscopic features could be correlated with clinical behavior. The majority of these lesions were asymptomatic and relatively innocuous. However, some displayed a more aggressive clinical course characterized by root resorption, pain or paresthesia, and cortical perforation. The over-all recurrence rate in the 142 cases was 16%. Adequate follow-up information (mean, 48 months) was only obtained for 47 patients, and 23 (46%) of these experienced one or more recurrences. Statistically significant histologic differences in distribution of giant cells and frequency of osteoid within the lesions were found in lesions that recurred as opposed to those that did not. The concept that giant cell lesions of the jaws are not totally different entities from giant cell tumors is discussed.