The effects of industrial noise on resting heart rate and blood pressure were studied in 3 105 blue-collar workers. Heart rate and blood pressure were measured in different workers at various times during the workday. After controlling for several possible confounders, we found that resting heart rate in females was associated positively with noise intensity (p =.036) and with time of day (p =.054). In males, resting heart rate was associated with noise intensity; however, such association was related to time of day (p =.046). No such associations were found for blood pressure in either sex. We plotted the mean resting heart rate by time of day for workers exposed to high [≥ 80 db(A)] and low noise, and no difference was evident with respect to morning heart rate in either sex. After 4 h of noise exposure for males (and less time for females), individuals who were exposed to high noise had higher heart rates; however, in females this was not observed at the end of the workday. Thus, recurrent daily exposure to high noise at work has an acute, though not residual, effect on resting heart rate.