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Rainfed agriculture in Jordan is one of the most vulnerable sectors to climate change, as the available water and land resources are limited and most of the country’s land is arid. In this study, a crop simulation model (DSSAT) was used to assess the impact of different climate change scenarios on rainfed wheat and barley in the Yarmouk basin in Jordan. Analysis of observed crop data showed differences between cultivated and harvested areas for both crops in the study area with variations among years. Results from DSSAT model for years showed that it was able to capture the trend of yield over the years realistically well. The model predicted an average yield of wheat of 1176 kg ha(-1), which was close to the average (1173 kg ha(-1)) obtained from the data of department of statistics (DOS), and an average predicted yield of barley was 927 kg ha(-1) while the DOS average was 922 kg ha(-1), with higher RMSE for barley (476 kg ha-1) than for wheat (319 kg ha(-1)). Results for predicting future yield of both crops showed that the responses of wheat and barley were different under different climate change scenarios. The reduction of rainfall by 10-20% reduced the expected yield by 4-8% for barley and 10-20% for wheat, respectively. The increase in rainfall by 10-20% increased the expected yield by 3-5% for barley and 9-18% for wheat, respectively. The increase of air temperature by 1, 2, 3 and 4 C resulted in deviation from expected yield by -14%, -28%, -38% and -46% for barley and -17%, +4%, +43% and +113% for wheat, respectively. These results indicated that barley would be more negatively affected by the climate change scenarios and therefore adaptation plans should prioritize the arid areas cultivated with this crop. (C) 2010 Elsevier Ltd. All rights reserved.