['In view of the recent increase in patients presenting with only 1 core positive for prostate carcinoma, we examined the correlation in tumor volume between the biopsy and the subsequent radical prostatectomy specimen.', 'We studied a total of 169 consecutive prostate biopsies with matched radical prostatectomy specimens and selected 48 patients with only 1 positive core.', 'Cancers found in the biopsy regardless of their size were associated with a wide range of cancer volume in the radical prostatectomy specimens, and the amount of cancer in the biopsy was a poor predictor of the volume of cancer in the prostatectomy specimen. Even with a cancer of 3 mm. or less in the biopsy, 57% of patients had cancer of clinically significant volume (greater than 0.5 ml.). Other modalities for the evaluation of prostate cancer such as Gleason score and clinical stage were not helpful in segregating patients with clinically significant from those with insignificant volume of cancer. However, when combined with a preoperative serum prostate-specific antigen higher than 10 ng./ml., 1 core positive biopsy could reliably predict the presence of cancer of significant volume.'] Is one core positive prostate biopsy a poor predictor of cancer volume in the radical prostatectomy specimen?