The keratolytic effect of salicylic acid was measured with a colorimeter after staining the outer layers of the stratum corneum with silver nitrate. Salicylic acid was used in a concentration of 5% or 10% in vaseline or of 5% in an improved vehicle. The results of two experiments showed that improvement of the vehicle increased the keratolytic effect of salicylic acid and that urea played a major role in this improvement.