The aim of the present study is to determine the applicability of three different sepiolite samples received from the Eskisehir region of Turkey in the production of desiccant clay. Japanese (JIS-Z-0701) and British (BS 3482-6) standards dictate that effective sepiolite should uptake humidity of at least 8% of its weight at 20% RH. This value must be 20% at 50% RH and 30% at 90% RH. Therefore, the HAC of sepiolites was modified by subjecting them to heat treatment at 200 degrees C and different relative humidity (RH) values of 20 to 90% as a function of time. The data obtained was interpreted on the basis of adsorption isotherms. The results indicate that raw sepiolites at 50% RH do not conform to the desiccant standards. Therefore, sepiolite/CaCl2 mixture at the different CaCl2 additions was evaluated for its potential as a humidity adsorbent. However, it is shown that sepiolite mixed with 5% CaCl2 at 50% RH or above exceeds the required specifications for a commercial desiccant. (C) 2010 Elsevier B.V. All rights reserved.