A study was conducted to determine if a two-dose regimen of influenza vaccine would enhance the immunologic response of 41 patients with lymphoma receiving chemotherapy. Hemagglutinin-inhibiting antibody responses to influenza A/H1N1, A/H3N2 and B virus occurred in 32%, 24% and 20% of patients following one dose, and in 49%, 41% and 46% of patients following two doses, respectively. Responses to one or more vaccine components occurred in 42% of patients after one dose and in 71% after two doses. Fifty percent of the patients who did not respond after one dose responded after two doses. A two-dose regimen of influenza immunization may significantly enhance the response rate of cancer patients receiving chemotherapy.