This study assessed the influence of short-term changes in smoking habit on blood levels of inflammatory markers, which have been associated with increased cardiovascular risk. Five inflammatory markers were measured before and 6 weeks after attempting smoking cessation in 138 healthy women. In the 48 participants who stopped smoking, white blood cell count (-0.7+/-1.2 x 10(9)/L; P<.001) and fibrinogen (-0.6+/-1.5 micromol/L; P<.01) decreased, but there was no significant (P>.1) change in the plasma level of C-reactive protein (median change +0.1; interquartile range -0.2, 0.9 mg/L), intercellular adhesion molecule 1 (+17+/-75 ng/mL), or CD40 ligand (+0.4+/-2.1 ng/mL). Most of the individual variation in inflammatory marker levels was unrelated to changes in smoking habit.