Thromboangiitis obliterans (TAO) has been reported to become less common in general population but more common in women, and in elderly patients. The authors looked at the clinical characteristics of TAO in Poland where there was no significant decrease of smoking and the extent of aging of the general population is less profound. They retrospectively reviewed the records of 377 patients with the diagnosis of TAO hospitalized in their institution from 1970 to 1995. If young smoking males demonstrated distal-extremity ischemia with no bruits audible over major arteries, upper limbs involvement, or superficial thrombophlebitis, the diagnosis of TAO was considered certain. When at least one of those criteria was missed, and in men older than 35 years, but in all females, typical arteriographic findings were required for the diagnosis of TAO. Connective-tissue disease, hyperlipidemia, diabetes, and hypercoagulable state were excluded. Three hundred forty-two men (91%), and 35 (9%) women had a mean age of 29.5 years at the onset of the disease (the oldest patient was 50 years old). The prevalence of TAO in southwest Poland is 8.1/100,000 and the incidence of the disease steadily declines; there was no increase of TAO in women. Three hundred thirty-seven (89%) experienced rest pain, 321 (85%) had ischemic necrosis, and 233 (62%) thrombophlebitis at some (continued on next page) time in the course of the disease. Raynaud's phenomenon occurred in only 39 patients (10%). Those patients who had quit smoking had a 50% decrease of the disease recurrences compared to their smoking period. Because the cause of declining incidence of TAO is obscure, the authors critically evaluated previously used explanations of this phenomenon. They did not confirm the observation of a change in the TAO clinical spectrum: occurrence in women did not increase, the aging of the TAO population was not observed. In Poland TAO is still a disease affecting the peripheral circulation of young smoking males with recurrent episodes of superficial thrombophlebitis and common involvement of the upper extremities; Raynaud's phenomenon is rather infrequent. Smoking cessation ameliorates the course of the disease but does not invariably stop further exacerbations.