Much evidence has accumulated indicating that cigarette smokers weigh less than non-smokers and that smokers gain weight when they cease smoking. In the present study we evaluated the effects of cigarette smoke and nicotine on food intake, weight gain, resting energy output, brown fat mass and opiate binding (opiates initiate feeding in sated rats) in rats. Chronic smoke exposure slightly suppressed growth rate and food intake after 14 days of smoke exposure. Blood glucose levels and intrascapular brown adipose mase were increased as a result of smoke exposure. Hamsters chronically exposed to cigarette smoke decreased body weight; however, food intake was not significantly suppressed. Short term (5 day) exposure to nicotine (4 and 2 mg/kg/day) suppressed growth rate and food intake. Nicotine (4 and 2 mg/kg) significantly suppressed water ingestion in water-deprived rats and altered the quantities of flavored solutions ingested by rats compared with those ingested by rats receiving no nicotine. Thus cigarette smoke and nicotine exposure affects food intake, energy utilization and taste perception; all parameters which contribute to overall body mass; however, these parameters change in a complex manner with only small changes occurring at specific time intervals.