Thirty-six cases of borrelial lymphocytoma were detected during the period 1986 to 1990 in Slovenia. Borrelial lymphocytoma was located on the ear lobe in 17 persons, ten female and seven male, with a median age of 12 years (range 2-56). Fourteen of these 17 were children under 14 years of age. A tick bite was remembered by 15 patients a median of 30 days before borrelial lymphocytoma developed. The most frequent month of onset was September. Erythema migrans preceded or accompanied borrelial lymphocytoma in eight cases. In 15 cases, eight female and seven male, borrelial lymphocytoma was localized on the mamilla. Median age of these patients was 42 years (range 15-72). Twelve had a tick bite about 45 days (median value) before the onset of borrelial lymphocytoma, which occurred most frequently in August. Erythema migrans was reported in 13 patients and preceded borrelial lymphocytoma in ten cases. In another four patients borrelial lymphocytoma was localized on the nose, scrotum, upper arm and shoulder. Antibiotic treatment with phenoxymethyl-penicillin (n = 16), ceftriaxone (n = 8), doxycycline (n = 9), azithromycin (n = 2) and penicillin G (1) led to complete recovery within an average of three weeks in all cases.