Our goal was to establish two new predictive models of prostate cancer to determine whether to require a prostate biopsy when the prostate-specific antigen level is in the diagnostic gray zone.A retrospective analysis of 197 patients undergoing prostate biopsy with prostate-specific antigens between 4 and 10 ng ml-1 was conducted.Of these,47 patients were confirmed to have cancer,while the remaining 150 patients were diagnosed with benign prostate disease after examining biopsy pathology.Two multivariate logistic regression models were established including age,prostate volumes,free/total prostate-specific antigen ratio,and prostate-specific antigen density using SPSS 19.0 to obtain the predicted probability and Logit P,and then,two receiver operating characteristic (ROC) curves were drawn to obtain the best cutoff value for prostate biopsy:one for the group of all the prostate cancers and one for the group of clinically significant prostate cancers.The best cutoff value for prostate biopsy was 0.25 from the multivariate logistic regression ROC curve model of all the prostate cancers,which gave a sensitivity of 75.4％ and a specificity of 75.8％.The best cutoff value for prostate biopsy was 0.20 from the multivariate logistic regression model of clinically significant prostate cancers,which gave a sensitivity of 76.7％ and a specificity of 80.1％.We identified the best cutoff values for prostate biopsy (0.25 for all prostate cancers and 0.20 for clinically significant prostate cancers) to determine whether to require prostate biopsy when the PSA level is in the diagnostic gray zone.