The ability to estimate prostate weight is useful. Two commonly used methods for estimating prostate weight are digital rectal examination (DRE) and transrectal ultrasonography (TRUS). We evaluated the relative accuracy of these weight estimates by comparing them to prostate weight following radical retropubic prostatectomy (RRP). Between 1989 and 2001 more than 36,000 community men participated in a large prostate cancer screening study. Of these men 2,238 underwent RRP. In this subset we examined the correlation between documented preoperative DRE and TRUS estimates of prostate weight with actual gland weight. DRE estimates of prostate weight by multiple examiners correlated poorly with RRP specimen weight (r = 0.2743). However, TRUS estimates correlated moderately well (r = 0.6493). TRUS provided more accurate estimates of prostate weight for smaller glands, although it generally underestimated gland weight compared to the weight of the surgical specimen. In a large, community based prostate cancer screening study prostate weight estimated by DRE was shown to correlate poorly with actual prostate weight. Compared with DRE, TRUS provides a better estimate of prostate weight. In addition, TRUS measurements were more accurate in smaller prostate glands.