BACKGROUND: Medicare reimbursement cuts have been associated with declining gonadotropin-releasing hormone (GnRH) agonist overuse in localized prostate cancer. Medical school affiliation and foreign training have been associated with persistent overuse. However, physician-level prescribing changes and the practice type of persistent overusers have not been examined. We sought to describe physician-level changes in GnRH agonist overuse and test the association of time in practice and solo practice type with GnRH agonist overuse. METHODS: We matched American Medical Association physician data for 2138 urologists to Surveillance, Epidemiology and End Result-Medicare data for 12,943 men diagnosed with early-stage and lower-grade adenocarcinoma of the prostate between 2000 and 2007. We conducted a population-based, retrospective study using multilevel modeling to control for patient and provider characteristics. RESULTS: Three distinct patterns of GnRH agonist overuse were observed. Urologists' time in practice was not associated with GnRH agonist overuse (odds ratio (OR) 0.89; 95% confidence interval (CI): 0.75-1.05). However, solo practice type (OR 1.65; 95% CI: 1.34-2.02), medical school affiliation (OR 0.65; 95% CI: 0.55-0.77) and patient race were. Compared with non-Hispanic whites, non-Hispanic blacks (OR 1.76; 95% CI: 1.37-2.27), Hispanics (OR 1.41; 95% CI: 1.12-1.79) and men of 'other' race (OR 1.44; 95% CI: 1.04-1.99) had greater odds of receiving unnecessary GnRH agonists. CONCLUSIONS: GnRH agonist overuse remains high among some urologists who may be professionally isolated and difficult to reach. These urologists treat more vulnerable populations, which may contribute to health disparities in prostate cancer treatment quality. Nonetheless, these findings provide guidance to develop interventions to address overuse in prostate cancer.