The objective of this study was to evaluate and compare the immunogenicity, safety, and tolerability of two influenza subunit vaccines, a primarily European-marketed trivalent vaccine (Agrippal®, Novartis Vaccines), and a predominantly U.S.-marketed control trivalent vaccine (Fluvirin®, Novartis Vaccines), in subjects aged 3-64 y. The immunogenicity of both vaccines was evaluated according to the Center for Biologics Evaluation and Research (CBER) criteria. This clinical trial was performed between April and December 2007 in Argentina. A total of 1893 subjects were stratified into three age groups (3-8 y, 9-17 y, and 18-64 y), and randomized in a 2:1 ratio to receive either Agrippal or Fluvirin. Adolescents and adults received one dose of vaccine intramuscularly, whereas children aged 3-8 years received two vaccine doses, administered 4 wk apart. Antibody levels were measured by means of hemagglutination inhibition assay before vaccination (baseline); 21 d after the first vaccination (adults and adolescents); and, for children aged 3-8 y, 28 d after the first vaccination and 21 d after the second vaccine dose. Adverse reactions were solicited via diary cards for 7 d after each vaccination, and unsolicited adverse events were reported throughout the study period. Both vaccines were safe and well-tolerated, and elicited robust immunogenic responses in all age groups, meeting both CBER licensure criteria for all three viral strains after completion of the age-recommended vaccination schedule. These findings support the use of the trivalent subunit influenza vaccines Agrippal and Fluvirin for universal vaccination campaigns on an annual basis. ClinicalTrials.gov: NCT00464672.