["What's known on the subject? and What does the study add? Positive surgical margins (PSMs) after radical prostatectomy are common, although their impact on the risk of disease recurrence is unknown. We examined the impact of PSMs on the risk of 'significant' biochemical recurrence stratified by their risk of occult metastatic disease. We find that only in intermediate-risk disease does the presence of a PSM have a significant impact on the risk of recurrence, and this represents a failure of technique. By contrast, for high- and low-risk disease, the risk of recurrence is driven by intrinsic tumour biology, and the presence of a PSM has little impact on outcome.", 'To determine the impact of surgical margin status on the risk of significant biochemical recurrence (prostate-specific antigen [PSA] doubling time <3, <6 or <9 months) after prostatectomy.', 'Patients undergoing radical prostatectomy with complete clinical and pathological data and detailed PSA follow-up were identified from two prospectively recorded databases. Patients were stratified according to their risk of occult systemic disease (low risk: PSA < 10 ng/dL, pT2 stage and Gleason score ≤6; intermediate risk: PSA 10-20 ng/dL, pT2 stage and/or Gleason score 7; high: PSA > 20 ng/dL or pT3-4 stage or Gleason score 8-10) and the impact of a positive surgical margin (PSM) within each stratum determined by univariable and multivariable analysis.', 'Of 1514 patients identified, 276 (18.2%), 761 (50.3%) and 477 (31.5%) were classified as having low-, intermediate- and high-risk disease respectively. A total of 370 (24.4%) patients had a PSM and with a median follow-up of 22.2 months, and 165 (7%) patients had a biochemical recurrence. Sufficient PSA data was available to calculate PSA doubling times in 151/165 patients (91.5%). The PSM rate rose significantly, from 11% in low-risk to 43% in high-risk disease (P < 0.001), with similar positive associations noted with tumour grade, stage and serum PSA (P < 0.001). Patients with low-risk disease had essentially identical risks of significant biochemical recurrence over the study period, regardless of surgical margin status. By contrast, in patients with both intermediate- and high-risk disease, a PSM was a strong predictor of significant biochemical recurrence on univariable analysis. On multivariable analysis, howver, PSM predicted significant disease recurrence in intermediate-risk disease only.'] Are positive surgical margins a risk factor for significant biochemical recurrence only in intermediate-risk disease?