Uncertainty regarding the benefits of pneumococcal vaccination may contribute to the under use of this vaccine. The present study was conducted to clarify the benefits of influenza and pneumococcal vaccinations during 3 influenza seasons among elderly persons with chronic lung disease. All elderly members of a large managed care organization with a prior diagnosis of chronic lung disease were included in a cohort that was followed over three influenza seasons (1993-1994, 1994-1995, and 1995-1996). Data obtained from the administrative data bases of the health care organization included baseline demographic and health characteristics, influenza vaccination status for each season, date of pneumococcal vaccination, and outcomes for each season including hospitalization for pneumonia and death. Cox proportional hazards regression and Poisson regression with repeated measures were used to compare the risk of outcomes among vaccinated and unvaccinated persons while controlling for covariates and confounders. During the three influenza seasons, influenza vaccination alone was associated with a 52% reduction (95% CI 18-72) in hospitalizations for pneumonia and a 70% reduction (95% CI 57- 89) in death. Pneumococcal vaccination alone during the three influenza seasons was associated with a 27% reduction (95% CI 13-52) in hospitalizations for pneumonia and a 34% reduction (95% CI 6-54) in death. Both vaccinations together demonstrated additive benefits. When both vaccinations had been received, there was a 63% reduction (95% CI 29-80) in hospitalizations for pneumonia and an 81% reduction (95% CI 68-88) in death versus when neither had been received. These findings suggest pneumococcal vaccination is associated with substantial benefits for elderly persons with chronic lung disease.