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Purpose: Exercise leads to a lower risk of coronary artery disease (CAD). However, whether time of day physical exercise has effects on CAD is still unclear. The present study is to investigate the relationship between time of day physical exercise and angiography determined CAD in a Chinese population. Subjects: A total of 1,129 consecutive participants who underwent coronary angiography for the first time were enrolled in our study. Participants were divided into non-CAD group and CAD group according to the result of coronary angiography. We used a predesigned questionnaire--the work-related activity, leisure-time activity, and physical exercise information were recorded in the form of self-reporting. Results: Doing physical exercise was associated with a reduced risk of CAD, after adjusting the established and potential confounders, with an adjusted odds ratio (OR) of 0.48 (95% CI, 0.35-0.67) compared with those who did not any physical exercise. Moreover, the risk of CAD could linearly decrease with increase of intensity, duration and frequency of exercise. Further stratification analysis revealed that the protective effects of exercise were more significant in the afternoon and evening group than in the morning and forenoon group. The adjusted ORs of doing physical exercise in morning, forenoon, afternoon, and evening groups were 0.53 (0.36-0.78), 0.51(0.27-0.96), 0.46(0.25-0.85), 0.43(0.28-0.66), respectively, compared with nonexerciser (p < .05). Conclusions: Doing physical exercise can decrease the risk of CAD, and exercising in the afternoon or evening may have more significant effects on the prevention of CAD than in other time of day. [ABSTRACT FROM AUTHOR]