Eight-two patients with solid tumors and lymphomas were immunized with New Jersey, Hong Kong, and Victoria influenza vaccines. Patients were divided into groups according to treatment: chemotherapy, radiotherapy, or no treatment. Four parameters were examined to assess the response to immunization: seroconversion, protective titer level, geometric mean titer, and response to multiple vaccines. Patients with lymphoma showed the lowest antibody response. Patients with solid tumors had antibody responses which were not significantly different from controls but were superior to lymphoma patients (p less than .01). Timing of chemotherapy, immunoglobulin levels, and lymphocyte counts did not appear to play a major role in determining the antibody response. Patients with neoplastic diseases should be immunized against the prevailing influenza virus. Patients with lymphoma should also receive antiviral prophylactic therapy during influenza epidemics.