157 Background: Adequate and representative enrollment in therapeutic clinical trials is important to an NCI cancer center. Clinical trial participation is a string of 6 sequential patient and physician decisions beginning with an available therapeutic trial to enrollment in the trial. Opportunities for participation may be lost at any one of these steps. The objective of this study was to calculate transitional probabilities that measure patient, especially minority patient, accrual to clinical trials at the Sidney Kimmel Comprehensive Cancer Center and to describe the barriers for those dropping out at each step. Methods: Records for “first visit” medical oncology patients seen by three SKCCC physicians from January to April 2010 were abstracted. Prostate cancer case reports from the hospital cancer registry and a medical record review provided age, race, Hispanic ethnicity, place of residence, tumor characteristics, and prior treatment history. At each transition step, we calculated the proportion of patients who remained enrollable. Results: Overall, prostate cancer clinical trial participation was 17% (16/94). Minority accrual was similar to Caucasian accrual at 19% and 17% , respectively. Retention at each step of trial participation was highest for “discussed” (98%), “enrolled” (94%), “eligibility” for available trials (79%), and “consented” (71%). Two bottlenecks were qualitatively identified: “trial availability” (65%) and “patient interest” (51%). Forty-two percent of those for whom there was no trial available were older than 70 years and 33% were patients with rising PSA after local therapy and hormone-naïve. The “patient interest” step was shaped primarily by disinterest due to distance to SKCCC (83%). Conclusions: For prostate cancer patients, recruitment to medical oncology clinical trials is robust. Minority patients however are only 17% of all patients seen and half drop out when no trial is available and half of those remaining judged distance to be a problem (hence, no interest). This study approach has clarified which factors are likely to be barriers to participation and is likely useful to making adjustments that can reduce identified barriers by adding to trial portfolio as an example.