Background : Several keratolytic agents have been used in many dirmatologic conditions such as callus, keratosis palmaris of plantaris, however the evaluation method of the effects of keratolytiic agents has not been good enough in clinical use. Object : We have conducted an investigation to measure the effect of several keratolytic agents using an in vitro model. Method : We measured the fegraded protein of keratin by the bui iet method after adding enzymes such as trypsin, pepsin and papain, and irritants, salicylic acid and sodii m lauryl sulfate to the collected callus. Result : The order of the keratolytic effect of the enzymes was trypsir >pepsin> papain. It was difficult to detect the keratolytic effect of salicylic acid becaues of color hiidrance and there was an increasing tendency of keratolyti effect of sodium lauryl sulfate, however it was prominent mainly at a high concentration. Conclusion : These results suggested that the potency of similar types of keratolytic enzymes such as pepsin, trypsin and papain can be possible. However it was not such a sitable model to check the potency of the keratolytic effect of salicylic acid and the eoncentration tevel may be an important factor for certain kinds of chemicals such as sodium lauryl sulfate. (Kor J Dermatol 1993; 31(3): 337-340)