OBJECTIVES: The objective of this study was to evaluate the effects of nicotine gum price on gum acquisition and smoking abstinence in an over-the-counter (OTC) setting. METHODS: Adult smokers (N = 270) were randomized to acquire nicotine gum from a study clinic for $20/box, $10/box, or without charge.  They were then followed at 2, 6, 12, and 26 weeks after their initial gum purchase.  At each time point, seven-day point-prevalent abstinence was assessed.  Negative binomial regression was used to model the number of acquired boxes of nicotine gum as a function of intervention group, time of follow-up, and the interaction of these two factors.  Smoking abstinence was modeled separately at each time point using exact multiple logistic regression.  All effectiveness analyses were performed by intent to treat. RESULTS: The mean (SD) number of boxes of gum acquired prior to the 2-week visit was 1.04 (1.21), 1.53 (1.48), and 4.01 (2.26) in the $20/box, $10/box, and $0/box arms, respectively.  The mean (SD) number of boxes acquired over the course of the study was 2.11 (3.89), 3.48 (6.69), and 11.42 (12.72) in the $20/box, $10/box, and $0/box arms, respectively.  Differences in the number of boxes of gum acquired across intervention groups and time points were statistically significant (p <0.001).  At 26 weeks, abstinence rates were 1.08%, 6.74%, and 10.47% in the $20/box, $10/box, and $0/box arms, respectively.  Relative to the $0/box arm, the OR [95% CI] for abstinence in the $20/box and $10/box arms was 0.094 [0.004, 0.590] and 0.620 [0.197, 1.845], respectively. CONCLUSIONS: This is the first study to demonstrate in an OTC setting that the price of nicotine replacement therapy has an effect not only on medication acquisition but also on medication effectiveness.  Price was also observed to have a deleterious effect on subject retention.