The risk of cardiovascular morbidity and mortality is greatly affected by cigarette smoking. In order to study the pressor response to smoking, 10 normotensive and 10 mild or moderate essential-hypertensive smokers (> 20 cigarettes daily) were compared with 2 comparable groups of non-smokers. All subjects were asked to smoke 4 cigarettes during 1 h; blood pressure (BP) and heart rate (HR) were monitored beat-to-beat by a non-invasive device (Finapres Ohmeda) during the smoking period and during the immediately preceding non-smoking hour. Furthermore, all subjects underwent 24-hour ambulatory BP monitoring. In all groups, each cigarette induced a similar and statistically significant increase from baseline for both BP and HR. The recovery from the marked rise in BP and HR was very slow so that in the smoking hours BP and HR were persistently higher than in non-smoking hours; there were no statistically significant differences between the four groups. During 24-hour ambulatory monitoring both normo- and hypertensive smokers showed higher BP values and higher BP variability in comparison with the respective non-smokers' group. In conclusion, smoking habits were associated with a persistent increase in BP in each group we studied, possibly contributing to a smoking-related cardiovascular risk.