To assess the vasodilator reserve in microcirculation, post-occlusive reactive hyperemia was examined in 21 chronic cigarette smokers (mean age; 50 +/- 7 years) and 21 non-smokers (mean age; 51 +/- 6 years), who were all healthy males. Reactive hyperemia was induced by occluding the digital artery at the base of the middle finger, and the increase in skin blood flow (delta flow) was analyzed with a laser Doppler flowmeter. Occlusion time was increased in a step-wise manner from 30 sec up to 300 sec. Baseline skin blood flow was similar in both groups (smoker, 27 +/- 9 ml/min/100 g; non-smoker, 25 +/- 10 ml/min/100 g, NS). The delta flow in smokers was significantly less (23%-59%) than that in non-smokers. Furthermore, the reduced delta flow in smokers was inversely correlated with Brinkmann's smoking index (r = 0.567, p < 0.01). These results indicate that chronic cigarette smoking impairs the microvascular response to transient ischemia, and that this impairment correlates with the intensity of the smoking habit.