OBJECTIVES:  Abiraterone was introduced in Quebec in 2012 for metastatic castration-resistant prostate cancer (mCRPC) in the post-docetaxel setting. This study described abiraterone utilization in the early post-approval period and its clinical effectiveness in Quebec, for both post-chemotherapy patients and patients unfit for chemotherapy METHODS:  A retrospective cohort study was conducted using Quebec public healthcare administrative databases. Our cohort consisted of mCRPC patients receiving abiraterone from 2012-2013 (N=303). The abiraterone group was stratified into abiraterone post-chemotherapy (N=99) and abiraterone without chemotherapy (N=204, unfit for chemotherapy and qualified for abiraterone with the “exception patient” measure). Study outcomes included overall survival, abiraterone duration, and hospitalization days. Cox proportional hazard regression was used to estimate the effectiveness of abiraterone in the post-docetaxel setting adjusted for several covariates. RESULTS:  Our cohort consisted of 303 mCRPC patients treated with abiraterone (abiraterone post-chemotherapy: 99 and abiraterone “exception patient”: 204). The median age was 75.0 for the abiraterone post-chemotherapy group and 80.0 for the abiraterone “exception patient” group. Median duration of abiraterone was 6 months (abiraterone post-chemotherapy: 5.3 months, abiraterone “exception patient”: 5.9 months). The corresponding median survivals were 12 and 14 months, respectively (log-rank test p-value=0.815). Risk of death was similar in the abiraterone post-chemotherapy and abiraterone “exception patient” groups (hazard ratio: 0.99; 95%CI 0.64-1.52). Hospitalization days were higher for abiraterone post-chemotherapy patients compared to abiraterone “exception patients” (13.7 vs 10.9 days, p-value=0.0096). CONCLUSIONS:  Effectiveness of abiraterone in older patients who were chemotherapy ineligible was similar to that of patients with prior docetaxel exposure. Overall, real-world survival benefits of abiraterone were similar to the results of the COU-AA-301 trial.