BACKGROUND: With the growing concerns about overtreatment in prostate cancer, the extent to which radiation oncologists and urologists perceive active surveillance (AS) as effective and recommend it to patients are unknown. OBJECTIVE: To assess opinions of radiation oncologists and urologists about their perceptions of AS and treatment recommendations for low-risk prostate cancer. RESEARCH DESIGN: National survey of specialists. PARTICIPANTS: Radiation oncologists and urologists practicing in the United States. MEASURES: A total of 1366 respondents were asked whether AS was effective and whether it was underused nationally, whether their patients were interested in AS, and treatment recommendations for low-risk prostate cancer. Pearson's chi test and multivariate logistic regression were used to test for differences in physician perceptions on AS and treatment recommendations. RESULTS: Overall, 717 (52.5%) of physicians completed the survey with minimal differences between specialties (P=0.92). Although most physicians reported that AS is effective (71.9%) and underused in the United States (80.0%), 71.0% stated that their patients were not interested in AS. For low-risk prostate cancer, more physicians recommended radical prostatectomy (44.9%) or brachytherapy (35.4%); fewer endorsed AS (22.1%). On multivariable analysis, urologists were more likely to recommend surgery [odds ratio (OR): 4.19; P<0.001] and AS (OR: 2.55; P<0.001), but less likely to recommend brachytherapy (OR: 0.13; P<0.001) and external beam radiation therapy (OR: 0.11; P<0.001) compared with radiation oncologists. CONCLUSIONS AND RELEVANCE: Most prostate cancer specialists in the United States believe AS effective and underused for low-risk prostate cancer, yet continue to recommend the primary treatments their specialties deliver.