The goal of the present study was to investigate the relation of hours of overtime work to cigarette consumption and addiction to cigarette, which was measured by the heaviness of smoking index. The subjects were 571 male daily smokers who responded to a cross-sectional survey of municipal employees of a Japanese city office, in which smoking was permitted in designated areas. Those who engaged in moderate overtime work (10-29 h per month) consumed less number of cigarettes per day and had lower levels of heaviness of smoking index, compared with those who worked either shorter or longer hours of overtime, although the differences were not statistically significant. In the workplace, men who worked 50 h or longer overtime last month consumed, on average, 4 cigarettes more than men who worked less than 30 h of overtime. Home cigarette consumption decreased as hours of overtime work increased. In stratified analysis, there was a significant difference in daily cigarette consumption according to hours of overtime work among smokers in staff position or under low psychological work stress; showing reduced consumption associated with medium levels of overtime work, compared to either no overtime work or extended overtime hours. The U-shaped relations of hours of overtime work to overall cigarette consumption and addiction to smoking deserve further investigations.