The results after 6 months of the treatment of three intervention groups with nicotine chewing gum to evaluate its effectiveness for the treatment of smoking addiction in primary care are reported. After random allocation, 106 individuals out of the 200 recruited in three health centers started the treatment. The active group (n = 37), treated with group sessions and nicotine chewing gum, was compared with a placebo group (n = 38) with an identical intervention. The success rate was 35.1 in the first group and 13.2 in the second (p less than 0.03), thus confirming the effectiveness of nicotine chewing gum. A third group, called consulting room group, (n = 31) was treated with nicotine chewing gum and follow up in the programmed usual consulting room. The rate of success in this group was 25.8%, without statistically significant difference with the first group.