Between 1999 and 2003 the Portuguese National Health Observatory, has conducted four telephone surveys (1998/99, 1999/00, 2001/02 and 2002/03) using the ECOS - Em Casa Observamos Saúde - panel of Portuguese families, with telephone aiming at studying the influenza vaccination coverage of the mainland Portuguese population. From the results it can be highlighted: The percentage of individuals that declared to have taken the influenza vaccine, showed a consistent increase between 1998/99 (14.2%) and 2001/02 (17.0%), and a decrease in 2002/03 (15.0%), without statistical significance. In 2002/03, the age group 65 years and older had the highest coverage of influenza vaccination (36.9%). The lowest percentage occurred in the 15 - 44 age group (7.0%). The individuals that declared to suffer from chronic diseases (asthma, rheumatic disease, hypertension and diabetes), showed higher coverage when compared with the general population. The highest values were verified in individuals that declared to suffer from diabetes (34.5%) and asthma (34.3%). Based on these results, it figures out important to promote a larger coverage of the influenza vaccination in the individuals with 65 years or more, once this coverage is not sufficiently high, if compared with the estimates from other European countries. Although there are no European estimates to compare with, it seems equally necessary to take measures to improve the coverage, in the risk groups studied, as well as in others risk groups that were not included the present study.