Trans-rectal ultrasound guided biopsy of the prostate represents the diagnostic standard for prostate cancer, but its mortality rate has never been examined. We performed a population-based study of 120-day mortality after prostate biopsy in 22,175 patients, who underwent prostate biopsy between 1989 and 2000. The control group consisted of 1,778 men aged 65-85 years (median 69.5), who did not undergo a biopsy. Univariable and multivariable logistic regression analyses were performed in 11,087 of 22,175 (50%) men subjected to prostate biopsy, to identify predictors of 120-day mortality. Variables were age at biopsy, baseline Charlson comorbidity index and cumulative number of biopsy procedures. We externally validated the model's predictors in the remaining 50% of men. Overall 120-day mortality after biopsy was 1.3% versus 0.3% (p < 0.001) in the control group. Of men aged < or = 60 years, 0.2% died within 120 days versus 2.5% aged 76-80. Zero Charlson comorbidity score yielded 0.7% mortality versus 2.2%, if 3-4. First ever biopsy procedures carried a higher mortality risk than subsequent procedures (1.4 vs. 0.8 vs. 0.6%). In the multivariable model, first ever biopsy, increasing age and comorbidity predicted higher mortality. Overall, the model's variables were 79% accurate in predicting the probability of 120-day mortality after biopsy. In conclusion, our data suggest that prostate biopsy might predispose to higher mortality rate. The certainty of this association remains to be proven.