Previous studies have shown that cotinine, a metabolite of nicotine, antagonizes some of the effects of nicotine. One study showed that nicotine eliminates some of the beneficial effects of the nicotine patch in reducing withdrawal symptoms. The purpose of this study was to examine the effects of cotinine. The results generally showed no effects on self-administration of cigarettes, although higher serum nicotine levels were observed on the highest doses of cotinine compared to placebo or lower doses of cotinine.