A study of morbidly obese patients was carried out to determine the frequency of preoperative smoking, the effect of smoking status on weight loss after vertical banded gastroplasty, and the effect of gastroplasty on postoperative smoking. There were 93 of 104 eligible patients (89.4 percent) available for study, 86 percent female and 14 percent male. All had a gastroplasty more than one year before with a mean follow-up of 22.9 +/- 7.8 months. Preoperative and postoperative weights were 124.4 +/- 19.5 kg and 89.4 +/- 17.9 kg for females and 156.5 +/- 22.3 kg and 102 +/- 17.4 kg for males. Preoperatively 38 percent smoked (females 36.7 percent, males 46.2 percent) and 57 percent were heavy smokers (greater than 25 cigarettes per day). Ten smokers quit postoperatively but seven nonsmokers started smoking. Those who smoked before operation lost more weight (43.26 kg) than nonsmokers (34.97 kg) and ex-smokers (32.41 kg); P less than 0.05. Those who smoked postoperatively lost more weight (44.47 kg) than nonsmokers (35.06 kg) and ex-smokers (33.07 kg); P less than 0.05. Because of the health risks of smoking, cessation is encouraged in spite of the advantage in weight loss for smokers after gastroplasty. More effective methods of controlling smoking and severe obesity are needed.