After topical application of commercial preparations containing heparin and heparinoids (MPS) in concentrations of 30,000 up to 150,000 IE/100 g, the individual layers of the skin show more or less increased heparinization, which can be traced by means of the permeation chamber technique. The average concentration of heparin and MPS in the dermal layers containing capillaries is about 0.1-0.5 IE/ml and 400-40,000 ng/ml, respectively, depending on the quality of the horny layer. We did not find any evidence for the permeation being activated either by DMSO, urea, or other accelerators. Repeated exposition to the preparation within 4 hours, however, resulted in increased permeation of heparin and MPS. The amount of the gel or ointment applied was of no significance.