Live influenza vaccines RIT 4025 and RIT 4050, containing the recombinants of A/Scotland/840/74 and A/Victoria/3/75 with A/PR/8/34 virus respectively, were administered during the vaccination campaigns 1975-76 and 1976-77 to patients with established chronic bronchopulmonary diseases. The study was designed to assess the clinical acceptability of these vaccinal strains and to measure the effects of vaccination on pulmonary function in this population. Clinical and respiratory function findings were compared in a control group of healthy volunteers. Good immunogenicity and good clinical tolerance were found in both populations. Pulmonary function tests had been performed before administration of the vaccine and repeated several times during the post-vaccinal period; the longest post-vaccinal follow-up of respiratory function in patients was four weeks. Apart from transient fluctuations, no significant changes in pulmonary function were found; results obtained in the group of patients were not different from those o0served in healthy subjects. These results correlate very well with observations reported with previous vaccinal strains (Ann and Alice) in pulmonary "high risk" patients.