A 10-fold increase of reported adverse events following influenza vaccination in the 1995-1996 campaign was reported. To evaluate the relative reactogenicity of different influenza vaccines a prospective observational study was conducted in 72 Italian local health units (LHU) in the period October-December 1996. Of the 16,637 enrolled individuals aged 65 or more, 27.4% reported the occurrence of at least one adverse event within 72 h of vaccination. The odds ratios, adjusted through a multivariate logistic model, were highest for whole vaccine recipients. Most of the observed events were of moderate clinical severity and were mainly represented by local symptoms. None of the products was found to show an unusual or concerning reactogenicity profile, and no severe events associated with immunization were reported.