Nylon-base radiochromic films (FWT-60(TM) and FWT-460(TM)) are commercially-available, thin dosimeters that are widely used in radiation processing. These films cover the following ranges of absorbed dose: 2 x 10(3) to 5 x 10(4) Gy for FWT-60(TM) and 5x10(3) Gy to 105 Gy for FWT-460(TM). Based on some earlier studies, their response functions have been reported to be dependent on the temperature and relative humidity during irradiation. The present study investigates differences in response over practical ranges of temperature, relative humidity, dose, and for different recent batches of films of both types. It is observed that for each new batch of film to be used for radiation processing, the effects of such parameters on response to both gamma rays and electrons should be investigated. It is also suggested that the films should be packaged under controlled atmospheric conditions (relative humidity) and should be calibrated under environmental conditions (temperature) at which they will be used routinely.