133 Background: Due to the growing concerns about over-diagnosis and overtreatment of localized prostate cancer (PCa), active surveillance (AS) has become an integral part of clinical practice guidelines. However, many men with low-risk PCa still receive primary therapy with surgery or radiation. Little is known about the barriers regarding the use of AS in clinical practice. To address this, we performed a national survey of radiation oncologists and urologists assessing the current attitudes and treatment for patients diagnosed with low-risk PCa. Methods: From January to July of 2017, 915 radiation oncologists and 940 urologists were surveyed about perceptions of AS for low-risk PCa. The survey queried respondents about their opinions and attitudes towards AS and treatment recommendations for a patient having low-risk PCa with clinical factors varying from patient age (55, 65 and 75 years old), PSA (4 and 8 ng per dl), and tumor volume for Gleason 3+3 disease (2, 4 and 6 cores). Pearson chi-square and multivariable logistic regression were used to identify respondent differences in treatment recommendations for low-risk PCa. Results: Overall, the response rate was 37.3% (n = 691) and similar for radiation oncologists and urologists (35.7% vs. 38.7%; p = 0.18). While both radiation oncologists and urologists viewed AS as effective for low-risk PCa (86.5% vs. 92.0%; p = 0.04), radiation oncologists were more likely to respond that AS increases patient anxiety (49.5% vs. 29.5%; p < 0.001). Overall, recommendations varied markedly based on patient age, PSA, number of cores positive for Gleason 3+3 prostate cancer and respondent specialty. For a 55-year-old male patient with a PSA 8 and 6 cores of Gleason 6 PCa, recommendations of AS were low for both radiation oncologists and urologists (4.4 % vs. 5.2%; adjusted OR: 0.6; p = 0.28). For a 75-year-old patient with a PSA 4 and 2 cores of Gleason 6 PCa, radiation oncologists and urologists most often recommended AS (89.6% vs. 83.4%; adjusted OR: 0.5; p = 0.07). Conclusions: While both radiation oncologists and urologists consider AS effective in the clinical management of low-risk PCa, its use varies markedly by patient age, PCa volume, PSA and physician specialty.