The ability of monophosphoryl lipid A (MPL), QS-21, and alum to alter the immunologic response to immunization with respiratory syncytial virus a chimeric FG construct (FG) subunit vaccine was examined in BALB c mice. FG MPL , FG/alum, and FG/MPL/QS-21 combinations increased non-neutralizing antibody response, while FG/QS-21 did not. FG subunit vaccine with MPL, QS-21, or both had cytokine responses more closely resembling primary infection than FG/alum, with decreased interleukin-4 mRNA levels and increased IgG2a isotype antibody. The lungs of the mice immunized with FG subunit vaccines showed a heightened inflammatory response to respiratory syncytial virus challenge as compared to live virus immunization. Adjuvants can be used to alter the humoral and cellular responses to RSV subunit immunization.