B- and T-cell responses have been studied after primary and secondary immunizations of mice with iscoms containing influenza virus envelope glycoproteins. After primary immunization both B- and T-cell responses were initiated in the draining lymph nodes. T-cells showed peak activity with respect to proliferation and cytokine production after five to eight days and the highest number of IgG secreting cells (IgG-SC) was recorded at day seven. The responses in the spleen developed slowly but were of longer duration. Cytokines produced by spleen cells included high levels of IFN-gamma and IL-2. After a secondary immunization the frequencies of IgG-SC were drastically increased in both LN and spleen, but decreased rapidly with time. At day eight after the secondary immunization high numbers of IgG-SC were detected in the bone marrow. High titres of IgG1 and IgG2a and substantial titres of IgG2b and IgG3 were detected in serum.