The percutaneous absorption of chlorquinaldol from three different preparations for skin treatment (Sterosan-hydrocortisone ointment and cream, Sterosan ointment) was evaluated by measuring the cumulative urinary excretion of chlorquinaldol and was compared to that found after an equivalent oral dose. In the blood the concentrations were below the detection limit of the analytical procedure, i.e., smaller than 0.02 μg/ml. The study was carried out in 3 healthy volunteers using a four-period change-over design. The topical preparations were applied under occlusive dressings. Following epicutaneous application of the three topicals in quantities containing 30 mg chlorquinaldol each, the mean urinary excretion of the drug amounted to 11.1 ± 6.6, 19.5 ± 3.5 and 13.0 ± 2.5% of the applied dose. When the same dose of chlorquinaldol was administered orally, 67.6 ± 9.5% of the dose was excreted in the urine. Taking the urinary elimination as the minimal amount of drug absorbed, the extent of percutaneous absorption from the three dermatological preparations varied between 4.2 and 23.5% of the applied dose. There was no difference in the pattern of urinary excretion products among the three topicals and the oral formulation. The bulk of chlorquinaldol (mean: 98.0 ± 0.1%) was excreted as glucuronide, and only small fractions were excreted as sulfate (mean: 1.3 ± 0.3%) or unchanged drug (mean• 0.8