Because smoking during pregnancy is implicated in influencing appetite and impulse control in offspring, the aim of this study was to establish if it is associated with bulimia nervosa in offspring. Bulimia was identified at age 30 years among 4046 females, born 5-11 April, 1970. After adjustment for potential confounding factors including body mass index (BMI) and maternal psychiatric morbidity, smoking during pregnancy was associated with bulimia in offspring by age 30 years. Compared with non-smoking mothers, the adjusted odds ratios (95% confidence intervals) for bulimia in offspring were 0.74 (0.25-2.21) for those who gave up before pregnancy, 3.04 (1.16-7.95) for giving up during pregnancy and 2.64 (1.47-4.74) for smoking throughout pregnancy. Smoking during pregnancy was not associated with anorexia nervosa in offspring. Neither BMI nor variation between childhood and adult BMI explain the association. If the association of smoking during pregnancy with bulimia in offspring is causal, then it may operate through compromised central nervous system development and its influence on impulse or appetite control. The increased risk associated with mothers who gave up smoking during pregnancy emphasizes the importance of smoking cessation prior to conception.