A total of 251 men with suspected prostate cancer were examined by transrectal ultrasound (TRUS) in order to evaluate the usefulness of TRUS and core biopsies for the detection of prostate cancer and determination of tumor volume, grade, and seminal vesicle invasion (SVI). Biopsies targeting hypoechoic lesions were taken in combination with systematic biopsies obtained from six standardized locations. Bilateral seminal vesicle biopsies were obtained from 168 of the men. A total of 26 patients underwent surgery and a comparison between the results of the histopathological evaluation of core biopsies and the prostatectomy specimen was performed. A total of 137 cancers were detected. In 34 patients (25%) the tumors were diagnosed by systematic biopsies alone. Tumor volume as estimated by TRUS underestimated the volume when compared to a planimetric technique. Correlation between the two methods was not found by regression analysis. Systematic biopsies did not improve grading compared to the grading of prostatectomy specimens. A total of 24 SVIs were detected. Valuable information was obtained for the diagnosis of prostate cancer by taking systematic biopsies.