Objectives: The theoretical threshold (effort-reward ratio >1.0) may not be ideal for the Japanese short version of the effort-reward imbalance (ERI) questionnaire. We aimed to seek the optimum cut-off point. Methods: We administered the original and short versions of the ERI questionnaire with a psychological distress scale to randomly selected workers (n=1,489) in a web-based survey. We evaluated kappa statistics and conducted receiver operating characteristics curve analyses. Cut-off values of the short version effort-reward ratios at 0.1 intervals in the range of 1.0-1.9 were tested using the criterion of an effort-reward ratio >1.0 for the original version. Results: The short version questionnaire had acceptable reliabilities. When using the theoretical cut-off point, the prevalence of high-risk groups was 63.2% for the short version compared with 18.9% for the original version, and their agreement was slight. Kappa agreements and receiver operating characteristics curve analyses suggested that a short-version effort-reward ratio of around 1.3 and 1.4 was the most equivalent to the original criterion. Regression equation procedures supported the findings, and ERI defined by the cut-off values showed significant associations with an external criterion (psychological distress) with minimal estimation error. Because the highest but only moderate kappa agreements with the risk group defined by the original criterion were obtained when setting 1.4-1.6 as the cut-offs, we considered >1.4 as optimal. Conclusions: This empirical investigation suggests the cut-off value of >1.4 for the Japanese short version of the ERI questionnaire screens out the ERI group with the most compatibility with the original version.(J Occup Health 2013; 55: 340-348)