Twenty-nine patients with systemic lupus erythematosus and 29 control subjects matched for age and prevaccination antibody titer received 200 chick-cell agglutinin units of A/New Jersey/76 HswINI influenza virus vaccine. Serum hemagglutination-inhibiting antibodies were measured before and 4 weeks after immunization. Clinical and laboratory evaluations were done before and 4 and 8 weeks after vaccination. Except for one patient with active lupus erythematosus who developed renal disease, there was no evidence of an increase in lupus erythematosus activity after immunization. Fourteen patients and 18 control subjects had a fourfold or greater increase in antibodies to influenza A/New Jersey/76. Mean postvaccination antibody titer of patients tended to be lower than that of controls (Student's t-test, t = 1.52, 0.05 less than p less than 0.10). Since patients with lupus erythematosus may have increased morbidity and mortality with influenza infections, they should receive influenza immunization even though the magnitude of their antibody response may be less than that of normal persons.