Eleven years after Lung Health Study (LHS) entry, we performed spirometry in 77.4% of surviving participants who enrolled in a long-term follow-up study. Those not enrolling tended to be younger male heavy smokers who continued to smoke during the LHS. Their initial LHS lung function, after adjustment for these factors, did not differ from that of enrollees. Smoking habits by original LHS treatment groups (smoking intervention vs. usual care) tended to converge, but 93% of participants who were abstinent throughout the LHS were still abstinent at 11 years. Differences in lung function between treatment groups persisted; smoking intervention participants had less decline in FEV(1) than usual care participants. Men who quit at the beginning of the LHS had an FEV(1) rate of decline of 30.2 ml/year, whereas women who quit declined at 21.5 ml/year. Men continuing to smoke throughout the 11 years declined by 66.1 ml/year, and women continuing to smoke declined by 54.2 ml/year. When decline in FEV(1) was expressed as a percentage of predicted normal value, no significant sex-based difference was apparent among continuing smokers. At 11 years, 38% of continuing smokers had an FEV(1) less than 60% of the predicted normal value compared with 10% of sustained quitters.