It is not clear whether there is a dose-response relationship between the number of cigarettes smoked per day and CRP level and whether there is a relationship between the length of smoking cessation and CRP level. Geometric mean levels of CRP were compared in smoking status groups for 1926 men aged 40 to 69 years using analysis of covariance. After adjusting for several confounding factors, geometric mean levels of CRP (mg/L) were significantly different among the three smoking status groups (0.41 in non-smokers, 0.57 in current smokers, 0.48 in past smokers, P < 0.05). A linear trend was not found in the relationship between CRP level and number of cigarettes smoked per day. The mean CRP level in the long cessation (> or =5 years) group was significantly lower than that in the short cessation (<5 years) group (0.45 vs. 0.58, P < 0.05) and similar to that in the non-smokers group (0.45 vs. 0.41, NS). CRP levels in current smokers are elevated but unrelated to the number of cigarettes smoked per day. In past smokers, long-term smoking cessation may contribute to the reduction in risk of development of cardiovascular diseases through inflammatory mechanisms.