OBJECTIVE: In 1999 we lowered the prostate-specific antigen (PSA) threshold for prostate biopsy at our institution from 4 to 2.5 ng/ml. The aim of this study was to compare the differences in tumor characteristics of the detected prostate cancers (PCAs) and the detection rate for the two different PSA thresholds and to evaluate if lowering the threshold was justified by any of the detected differences. PATIENTS AND METHODS: We retrospectively analyzed the records of all patients who underwent an 8-core prostate biopsy between January 1999 and December 2004 and had a PSA between 2.5 and 10 ng/ml. Patients with a PSA between 2.5 and 4 ng/ml (group 1, n = 214, mean age 62.0 years) were compared to patients whose PSA was between 4 and 10 ng/ml (group 2, n = 292, mean age 63.2 years). Patients who were older than 75 years or had a suspicious rectal examination were excluded from this study. RESULTS: Overall, we detected 120 can-cers in 506 patients (cancer yield 23.7%). The cancer yield in group 1 was significantly lower than in group 2 (17 vs. 28%, p < 0.01). In group 1 significantly less Gleason score >or=7 (p = 0.04) and significantly more potentially insignificant cancers (p = 0.03) were identified. In 80 patients who subsequently underwent radical prostatectomy, final pathology revealed no significant differences between the two PSA groups with regard to high pT stages, Gleason score >or=7 PCA or positive surgical margins, respectively. The difference in the absolute risk of being diagnosed with high-grade PCA between a PSA threshold of 2.5 ng/ml and a PSA threshold of 4 ng/ml was 1%. CONCLUSION: Lowering the PSA threshold for prostate biopsy from 4 to 2.5 ng/ml results in a substantial increase in the number of men who undergo biopsy and may result in an increased detection of potentially insignificant cancers. If total PSA alone is used to determine the need for prostate biopsy, the disadvantages of this lower threshold probably outweigh its potential benefits.