The hypothesis that weight concerns are related to less successful smoking cessation and greater relapse among ex-smokers was prospectively evaluated. A population-based sample of 4981 working women and men 17 to 71 years of age was surveyed at 32 work sites. Current and previous weight loss efforts and smoking behavior were self-reported at baseline and 2 years later. Dieting and weight concerns were unrelated to smoking cessation or relapse. However, female smokers who had previously participated in a formal weight control program were three times more likely to quit smoking than those without a history of participation (25% vs 11%; odds ratio = 3.25, 95% confidence interval = 1.86, 5.67). Weight concerns and dieting efforts do not appear to inhibit smoking cessation or increase relapse in adults.