['Routine sampling of the transition zone during prostate biopsy has become increasingly common. Although approximately 10% of prostate cancers originate in the transition zone, the benefit of transition zone biopsies may be limited. We evaluated the usefulness of transition zone biopsy in patients with prostate cancer enrolled in active surveillance.', 'Patients on active surveillance followed at our institution between 1993 and 2011 were identified in the urological oncology database. All surveillance biopsies were stratified by transition and peripheral zone pathology results. The usefulness of transition zone biopsy was assessed by whether transition zone specific cancer characteristics, eg volume and grade, changed disease management recommendations.', 'A single surgeon performed a total of 244 prostate biopsies in 92 men. Each patient underwent initial positive prostate biopsy and at least 1 active surveillance prostate biopsy. Mean age was 69 years. A mean of 2.7 biopsies were done per patient. Nine patients (10%) had positive transition zone cores on initial positive prostate biopsy, of whom 3 had transition zone unique cancers. One of these patients showed transition zone disease progression on active surveillance prostate biopsy, which led to up staging and exclusion from active surveillance. A total of 16 patients (17%) had positive transition zone cores on active surveillance prostate biopsy, of whom 13 had a negative transition zone on initial positive prostate biopsy. Transition and peripheral zone Gleason scores were identical in 9 of these patients and the transition zone score was lower in 4. Thus, transition zone pathology did not result in up staging or disease management alterations in any patient with new transition zone pathology.'] Does routine transition zone biopsy during active surveillance for prostate cancer rarely provide unique evidence of disease progression?