Male Wistar albino rats, bred and fed under standard laboratory conditions, were administered for 20 days two dosages [Group 1: 750 mg/kg body weight (n = 15) and Group II: 1500 mg/kg body weight (n = 15)] of oral hexachlorobenzene resolved in corn oil. Control group animals (n = 15) received only corn oil for 20 days. Twenty-four hours after the administration of the last dose, renal tissue samples, obtained by laparotomy, were fixed in 3% glutaraldehyde in phosphate buffer and 1% aqueous osmium tetroxide. Following the routine tissue processing steps, samples were blocked in Araldyte CY 212. Ultrathin sections taken by LKB V ultratome were stained with uranyl acetate-lead citrate and evaluated under a JEOL 100C transmission electron microscope.