Skin and nerve biopsies from 81 patients clinically suspected to have leprosy were studied. Histologically 54% of the patients showed leprosy. Both nerve and skin biopsies were histologically diagnostic of leprosy in 64% of these cases while 32% were diagnostic in the nerve but not skin biopsy. In the 11 patients with multibacillary leprosy (BI greater than or equal to 2) a multibacillary picture was seen in all nerve biopsies while 8 patients exhibited a paucibacillary leprosy of the skin and a multibacillary leprosy in the nerve. The present results emphasize that leprosy is a disease of peripheral nerves and that diagnostic criteria other than skin parameters is important to reach a proper diagnosis. The evident possibility of having patients with a multibacillary leprosy in peripheral nerves and paucibacillary in skin emphasize the need of clinical studies to clarify the criteria for the diagnosis of paucibacillary leprosy and the drug regimen for this group of patients.