Abstract.The MACROS crop model was evaluated for its utility to generate information on land suitability for dry season peanut cropping based on water availability at the regional scale in Khon Kaen Province, Northeast Thailand. The model was specific for the condition where crop growth is limited by water stress, and evaluated using both calibration and validation phases in sequence. In the model calibration, data sets from one peanut field experiment were used to calibrate some parameters to obtain the best agreement between experimental and simulated results. The model validation, in this study, consisted of a ‘validation A’, with emphasis on the accuracy and a ‘validation B’, with emphasis on the usefulness and relevance of the model. In the model validation A, data sets from peanut field experiments were used to validate the model under different conditions. Satisfactory agreements were found between the dynamics of observed and corresponding simulated values of shoot dry weight in every condition involved in this validation study. Also the simulated pod yields agree well with the field data. For the validation R, the model was further validated using data from 36 farm trials conducted at 5 different test sites. A high positive correlation (r= 0.91) existed between observed and simulated pod yields. Because of these satisfactory agreements between observed and corresponding simulated values, it was concluded that the model is valid and can be applied to Khon Kaen P