Data are reported on the heart rates of nine smokers who underwent 5 weeks of abstinence. There was an initial fall of 9.1 beats per min from 79 to 69.9 beats per min on the 1st day, with no significant change thereafter. The average heart rates after 2, 3, 4 and 5 weeks were 69.1, 69.1, 71.7 and 69.9 beats per min, respectively. Heart rate after 5 weeks was still significantly below baseline. The results indicate that the drop in heart rate which occurs open smoking abstinence is either a permanent change, or if it is a temporary withdrawal effect lasts longer than 5 weeks. If it is a permanent change then it may not make sense to consider drop in heart rate as part of a withdrawal syndrome; it could merely reflect absence of nicotine's stimulant action.