8 Background: To provide patients and clinicians more accurate estimates of co-morbidity specific survival stratified by patient age, tumor stage and tumor grade. Methods: We conducted a ten year competing risk analysis of 19,639 men age 66 years and older identified by the Surveillance, Epidemiology and End Results (SEER) program linked to Medicare program files. All men were diagnosed with localized prostate cancer and received no surgery or radiation within 180 days of diagnosis. The analysis was stratified by tumor grade and stage and by age and co-morbidity at diagnosis classified using the Charlson co-morbidity index. Underlying causes of death were obtained from SEER. Results: During the first ten years following diagnosis men with moderately and poorly differentiated prostate cancer were more likely to die from causes other than their disease. For men age 66-74 years with stage T1c Gleason score 5-7 disease at diagnosis, ten year overall mortality rates and prostate cancer specific rates were 28.8%, 50.5%, 83.1% and 4.8%, 2.0%, 5.3% respectively for men with Charlson scores 0, 1 and > 2. For men age 66-74 years with T1c Gleason score 8-10 disease at diagnosis, the corresponding rates were 55.0%, 52.0%, 64.3% and 25.7%, 20.2%, 13.7% respectively for men with Charlson scores 0, 1, > 2. Death from competing medical hazards was roughly comparable for men with stage T2 disease and higher for all men over age 75. Conclusions: Patients and clinicians should consider using co-morbidity specific data to estimate the threat posed by localized prostate cancer. No significant financial relationships to disclose.