We have studied the penetration in vitro of methanol and ethanol through excised, full thickness, guinea-pig skin. The total amount of methanol or ethanol that penetrated the skin over a period of 19 hr was in the order of 1% of the total dose. Neither compound appeared to show an increase in penetration with increasing dose volume. Penetration of both methanol and ethanol was significantly enhanced by occlusion. The amounts of both compounds that penetrated, and the profiles of the amount penetrating per hour, were significantly influenced by the nature of the occlusive material. Under occlusion and in the presence of either compound the barrier properties of the skin appeared to be altered so that 'fluid' was lost from or through the skin to the air space bounded by the occlusive material.