The frequencies of clinical features of Behcet's disease vary in different studies according to the diagnostic criteria used in the study, the department where the study is done, and the ethnic origin of patients included in the study. In this study, we aimed to evaluate the influence of the length of the follow-up period of patients on the frequencies of clinical features of Behcet's disease. Out of 231 patients who applied to our dermatology clinic from June of 1991 to October of 1996, only 52 patients that were followed up for at least five years were included in this retrospective study. The baseline characteristics of these 52 patients were almost the same as those of the 179 patients who dropped out. Almost all of the frequencies of clinical features at the end of the follow-up period of five years were higher than those at the time of presentation. The most prominent increases were observed for erythema nodosum (59.6% to 75.0%), papulopustular lesions (84.6% to 94.2%), and large vessel involvement (23.1% to 30.8%). According to our results, it is most likely that studies mainly including mostly patients with long-standing disease will report higher figures for the frequencies of these clinical features of Behcet's disease.