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Abstract: Cucumber downy mildew, caused by the fungal pathogen Pseudoperonospora cubensis, is a devastating disease in Shanxi Province, China. Fungicides dimethomorph, metalaxyl and fosetyl-aluminium have been used in the disease management. In this study, 143 isolates of P. cubensis were collected from different geographic locations of Shanxi, and examined for their corresponding sensitivities to these fungicides using the leaf disc bioassay method. The EC50 values of the isolates to dimethomorph, metalaxyl and fosetyl-aluminium ranged from 0.0006 to 5.85 μg/ml (mean = 1.01 μg/ml, SD = 1.27), 0.0869 to >500.00 μg/ml (mean = 85.97 μg/ml, SD = 95.61 for the range of 0.0869–458.10 μg/ml) and 0.0066–114.50 μg/ml (mean = 7.89 μg/ml, SD = 15.33), respectively. Over 80% isolates showed the EC50 values to dimethomorph <2.0 μg/ml. This study is the first to report high levels of resistance to metalaxyl in P. cubensis populations in Shanxi Province, and seven isolates were found to be extremely high resistant with EC50 values >500 μg/ml. The most P. cubensis isolates showed a normal distribution of EC50 range between 0 and 18 μg/ml to fosetyl-aluminium, and a few high resistant isolates were found. No cross-resistance was found between any fungicides used in this study. The concept of resistance index (RI) was used to determine the resistance level to each fungicide for sub-population of the pathogen in each district of Shanxi Province. [Copyright &y& Elsevier]