To assess whether the addition of clinical Gleason score (Gs) 3+4 to the Prostate Cancer Research International: Active Surveillance (PRIAS) criteria affects pathologic results in patients who are potentially suitable for active surveillance (AS) and to identify possible clinical predictors of unfavourable outcome. Three hundred and twenty-nine men who underwent radical prostatectomy with complete clinical and follow-up data and who would have fulfilled the inclusion criteria of the PRIAS protocol at the time of biopsy except for the addition of biopsy Gs=3+4 and with at least 10 cores taken have been evaluated. One experienced genitourinary pathologist selected those with real Gs=3+3 and 3+4 in only one core according to the 2005 International Society of Urological Pathology criteria. The primary end point was the proportion of unfavourable outcome (nonorgan confined disease or Gs⩾4+3). Logistic regressions explored the association between preoperative characteristics and the primary end point. Two hundred and four patients were evaluated and 46 (22.5%) patients harboured unfavourable disease at final pathology. After a median follow-up of 73.5 months, there was no cancer-specific death, and 4 (2.0%) patients had biochemical relapse. There were no significant differences in terms of high Gs, locally advanced disease, unfavourable disease and biochemical relapse-free survival among patients with clinical Gs=3+3 vs Gs=3+4. At multivariable analysis, the presence of atypical small acinar proliferation (ASAP) and lower number of core taken were independently associated with a higher risk of unfavourable disease. The inclusion of Gs=3+4 in patients suitable to AS does not enhance the risk of unfavourable disease after radical prostatectomy. Additional factors such as number of cores taken and the presence of ASAP should be considered in patients suitable for AS.