Purpose: We investigated biochemical outcomes following radical prostatectomy across subclassifications of clinical stage T1 prostate cancer. Material and Methods: Of 8,658 men who underwent radical prostatectomy for clinical stage T1 prostate cancer 85, 156 and 8,417 had clinical stage T1a, T1b and T1c disease, respectively. Age, race, prostate specific antigen, year of surgery and preoperative Gleason scores were compared across clinical stage T1 subcategories. Time to prostate specific antigen recurrence was compared among groups using Kaplan-Meier and Cox hazards modeling. Results: Patients with clinical stage T1a prostate cancer had more favorable postoperative pathological features, including lower prostatectomy Gleason scores (p <0.001), rates of extraprostatic extension (p <0.001), lymph node invasion (p <0.001) and positive surgical margins (p = 0.006). Patients with T1a cancer also showed significantly lower rates of biochemical recurrence on Kaplan-Meier analysis than men with T1b and T1c disease (log rank 0.006). Cox regression analysis adjusted for known predictors of biochemical recurrence demonstrated that clinical tumor stage in the subgroup of patients with T1 disease was not an independent predictor of biochemical recurrence (p = 0.321). Conclusions: Men with clinical stage T1a prostate cancer who undergo radical prostatectomy have significantly lower biochemical recurrence rates than men with stage T1b or T1c disease. However, subclassification of tumors in this group of patients was not an independent prognostic factor for biochemical recurrence after accounting for preoperative variables, including prostate specific antigen and Gleason score. © 2007 American Urological Association.