METHODS. One hundred six smokers seen in a family practice received brief physician advice and a prescription for nicotine gum. Smokers were randomly assigned to pay $20, $6, or $0/box of nicotine gum and followed for 6 months. RESULTS. Decreased cost increased the incidence of obtaining gum, the amount of gum used, and the incidence of long-term use (P less than 0.05). Decreased cost also increased cessation attempts and 1-week cessation (P less than 0.05) and appeared to increase abstinence at 6-month follow-up (19% vs 6% vs 8%, P less than 0.10). Cost-benefit estimates suggest that an insurance plan, HMO, etc., would recoup any costs in subsidizing nicotine gum and perhaps incur a net financial gain.