The authors assessed the impact of bother with urinary and bowel dysfunction on social activities among men in Japan and the United States following primary therapy for localized prostate cancer. In paired longitudinal outcomes studies, they measured general and disease-specific health-related quality of life in 400 Japanese and 427 American men who underwent radical prostatectomy, or brachytherapy, for localized prostate cancer. Among men who reported any urinary bother, Japanese men had slightly better urinary function than American men. Before brachytherapy, urinary bother was weakly correlated with social function in both the countries; after brachytherapy, urinary bother was strongly correlated with social function in American but not Japanese men. After brachytherapy, bowel dysfunction had a stronger correlation with social function in American than Japanese men. The bother associated with urinary and bowel dysfunction after surgery or brachytherapy for prostate cancer has a greater impact on social function in American men than in Japanese men.