Bivalent, live attenuated intranasally administered influenza A vaccines were compared to inactivated, parenterally administered influenza A vaccines in a double-blind clinical trial in 55 children and young adults with cystic fibrosis. No qualitative or quantitative difference in symptomatology between the group receiving intranasal live vaccine versus placebo was observed. Serum immune responses to live vaccines were somewhat less than those to inactivated vaccine, particularly in adults. IgA response in nasal secretions was minimal in each vaccine group. In contrast, an IgG response in nasal secretions was commonly seen with both topically applied live vaccine and parenterally administered inactivated vaccine.