Nicotine chewing gum is designed as an aid to smokers who intend to stop smoking. However, the efficacy of the gum in general medical practice has been questioned. This study describes the extent of nicotine chewing gum use among health maintenance organization members, the characteristics of prescribers and users, and the patterns of gum use over a two-year period. About 0.4 percent of Kaiser Permanente, Northwest Region members were exposed to the gum. Over the two-year observation period, 1970 members received at least one box (96 pieces) of the gum. Almost 70 percent of users received only one box of the gum. About 1.5 percent of users appeared to use the gum continuously at a daily dosage around the level needed to replace the nicotine addiction among most smokers, and for longer than the recommended three months. Another 2.5 percent appeared to use the gum continuously but at less than a nicotine-addiction replacement dose for longer than the recommended maximum of six months. The presence of a prepaid prescription drug benefit directly affected whether or not a person received the gum and how long he used it. The extreme variation in the patterns of use raises the questions of why the gum is used in this manner, and how effective it is when used in this manner.