Our findings suggest that influenza A(H1N1)pdm09 caused a significant burden of disease in Argentina during 2009. If we assume that influenza activity was similar throughout country, we could multiply the age specific influenza-associated rates from Santa Fe, Tucumán, and Mar del Plata and their 95% confidence intervals by the census population of Argentina (3,240,001 persons aged ,5 years; 25,055,187 aged 5-44 years; 7,717,549 aged 45-64; and 4,121,684 aged $65 years) to estimate that approximately 1,300,000 (95% CI 10,000,000-1,800,000) persons visited clini-cians for ILI, 10,000 (95% CI 13,000-7,200) were hospitalized, and 990 died (95% CI 1,100-970) throughout the country as a result of the 2009 pandemic.