The prognostic value of the erythrocyte sedimentation rate (ESR) was investigated in a population-based prostate cancer study, comparing 556 patients treated with no intent to cure. The data originated from hospital charts and death certificates. A statistically significant relationship between ESR at diagnosis and overall as well as disease-specific survival was demonstrated by univariate and multivariate analyses. A similar result was demonstrated in the 179 patients suffering from clinically organ-confined (T1-2,Nx,M0) disease. In a subpopulation consisting entirely of clinically organ-confined, small (T1), well-differentiated tumors, the dichotomized ESR (< or =20 mm/h vs. >20 mm/h) at the time of diagnosis distinguished between aggressive and non-aggressive tumors. In a small, second prostate cancer population it was demonstrated that ESR was not a surrogate marker for prostate- specific antigen (PSA). Our results indicate that ESR is a significant predictor of survival in early localized prostate cancer.