Purpose: Little is known about psychosocial factors affecting the decision to move from surveillance to active treatment in men with localized prostate cancer. We examined the impact of cancer anxiety on the decision to move from surveillance to treatment. Materials and Methods: We analyzed data from CaPSURE, a national observational prostate cancer registry. A total of 105 participants had localized disease, selected surveillance vs treatment and had at least 3 prostate specific antigen values available after baseline. Cancer anxiety was measured with a 3-item scale (α = 0.78). We calculated the rate of change in prostate specific antigen with time (prostate specific antigen velocity) and used the same formula to calculate the rate of change in cancer anxiety. We fit a Cox regression model to determine predictors of receiving treatment in the 3-year observation period, controlling for prostate specific antigen velocity, demographics and baseline clinical characteristics. Results: Prostate specific antigen velocity and the cancer anxiety change rate were significant independent predictors of treatment receipt (HR 1.02, 95% CI 1.004, 1.035, each p <0.01). Men with higher prostate specific antigen velocity (1.51 ng/ml per year or greater) were significantly more likely to receive treatment than men with lower prostate specific antigen velocity (HR 3.18, 95% CI 1.122, 9.016). The 2 velocity measures correlated only modestly (r = 0.29, p <0.001). Conclusions: Rather than being based only on clinical presentation and disease progression, decisions about treatment receipt for some men are influenced by cancer related anxiety. Men should be provided with more psychosocial support to perhaps delay treatment and the ensuing decrements in health related quality of life. © 2007 American Urological Association.