Evidence from survey-based studies suggests that monotonous work increases the risk of coronary heart disease (CHD). In this study of 1944 male and 832 female blue-collar workers aged 20-64 yr, we examined the association of CHD risk factors with two distinct objective work conditions--repetitive work (3 levels) and work underload-compared to varied work. After controlling for shift work, high ambient noise exposure and four other possible confounders, repetitive work was positively associated with both blood pressure and serum lipid levels in women, and with blood pressure in men. However, elevated levels of these risk factors were obtained only for those in short-cycle (< 1 min) repetitive work. In women this was manifested in higher mean systolic (p = 0.003), diastolic (p = 0.01) blood pressure (BP), total cholesterol (p = 0.03) and serum glucose (p = 0.05) levels; and in men in higher systolic BP only (p = 0.002). Inconsistent results were obtained for those engaged in work underload. It was associated in men with higher mean systolic BP (p = 0.05) and in women with higher cholesterol (p = 0.05) and high density lipoprotein (p = 0.03) levels. These findings suggest that objective monotonous work conditions are more consistently related to CHD risk factors in women, especially those engaged in short-cycle (hectic) repetitive work.