Basal cell carcinomas (BCC) are among the most common cancers in white subjects. Etiologic factors include ultraviolet and ionizing radiation, chemical carcinogens, and possibly infection with human papillomaviruses. Because of clinical and histologic differences, differential pathogenetic mechanisms have been suggested for different BCC subtypes. We studied the patient and tumor characteristics of all BCC diagnosed and/or treated at the departments of Dermatology and Plastic Surgery of our hospital between 1985 and 1996, and a review of the literature was carried out. Some important differences between patients with nodular BCC and patients with superficial BCC were observed. The frequency of superficial BCC was higher in females and was seen in younger patients as compared with nodular BCC. The latter occurred mainly in the head/neck region: in males they were seen more frequently on the ears, and in females they were predominantly seen on the eyelids, the lips, and in the neck. Superficial BCC occurred mainly on the trunk, and occurred significantly more often on the trunk in males than in females, where the legs were the most common site. These findings strongly suggest that the superficial subtype is a separate group within the clinical entity of BCC. Furthermore, our findings seem to support the etiologic role of sun exposure in these tumors; however, this role may be different for each subtype. Chronic sun exposure may be an etiologic factor in nodular BCC as compared with intermittent sun exposure in superficial BCC. Other factors, such as differences in site specific host factors and referral bias, may also play a role in the differences found between the subtypes.