The aim of this study was to examine any dose response effect of 2 and 4 mg nicotine gum (Nicorette) as well as the effect of the treatment in relation to a control group. One hundred seventy-two cigarette smokers were randomly allocated to group counselling and 2 mg- (n = 62) or 4 mg- (n = 54) nicotine chewing gum or to an "advice only" control group (n = 56). Six group meetings in a three month period were guided by physicians in groups of 10-12 members. The 4 mg gum was replaced by 2 mg after 4 weeks. The overall chemical verified success rate was significantly higher for the treatment group compared with the control group. The success rate for the gum group was 45.6% after three months versus 7.1% for the control group, 33.3% versus 3.7% after 12 months, and 27.2% versus 5.7% after 22 months, respectively (p less than 0.001). We could not demonstrate any significant dose response effect of 2 and 4 mg nicotine gum. The low dependent smokers had the best outcome. The subgroup of self-reported chronic bronchitis subjects had a significantly lower success rate than their healthy counterparts (p less than 0.002). Neither the p-nicotine level after smoking or chewing gum nor the difference between these two could predict the outcome. The gum p-nicotine after a week was only 37.1% for 2 mg and 64.3% for 4 mg of the corresponding smoking p-nicotine levels. Nicotine compensation was best for the high dependent smokers.