To evaluate whether a single positive prostate biopsy in six systematic transrectal ultrasonography (TRUS)-guided biopsies is predictive of a small tumour volume in a subsequent radical prostatectomy (RP) specimen.Of 158 patients submitted to RP for T1-T2 prostate cancer, 15.2% had one positive biopsy. The rate of positive margins (M+) and extra-capsular involvement (C+) were assessed on the RP specimen in those with one positive biopsy (group I) and in those diagnosed by more than one positive biopsy (group II). The percentage of those with postoperative biological progression (P+), having a prostate-specific antigen (PSA) level > 0.1 ng/mL, was evaluated in both groups. The Gleason scores in biopsies and specimens were also compared. Fifteen patients diagnosed by a single positive biopsy were management conservatively.The percentage of patients who were categorized C+, M+ and P+ was 29.2, 16.7 and 26% in group I and 70, 46.5 and 49.5%, respectively, in group II. All patients with < 10% of the biopsy core length invaded by cancer had intracapsular (P2) disease, whereas if all the core length was invaded by tumour, all patients had extracapsular (P3) disease. The Gleason scores for biopsy cores and whole specimens were identical in 38.7% of the cases; the Gleason score was underestimated on biopsy in 48.4% of cases. In the group treated conservatively, nine of 15 patients were in biological progression, with a mean follow-up of 22 months.A single positive needle-biopsy in six systematic TRUS-guided prostate biopsies is not predictive of low-volume prostate cancer on an individual basis and does not guarantee a favourable outcome after RP.