Humidity sensitive films with the structure of an interpenetrating network were prepared through simultaneous quaternization and crosslinking of poly(4-vinylpyridine) and poly(glycidyl methacrylate) with 1,4-dibromobutane and diethyltriamine, respectively, on the interdigital electrodes. The effect of the composition of humidity sensitive film and the concentration of dip-coating solution on the humidity sensitive properties of the sensors have been investigated. The humidity sensors so prepared exhibit little hysteresis (<1% RH [relative humidity]) and the response time for adsorption and desorption between 80% RH and 54% RH is about 21 s and 3 s, respectively, suggesting a very fast response. (C) 2007 Wiley Periodicals, Inc.