OBJECTIVE: The aims of this study were: (1) to evaluate the burden of influenza in terms of its impact on an individual’s normal daily activities (including ability to work); (2) to evaluate the beneficial effect of treatment with Oseltamivir on activity. METHODS: The impact of influenza on the individual was assessed by seven symptoms and a set of well-being indicators. These indicators include the self-rated parameters for general health, sleep quality, overall level of activity and paid work activity. This analysis is based on pooled data derived from two double-blind, randomized and stratified, placebo-controlled multi-centre studies conducted in the winter season 1997/1998. RESULTS: In the intent to treat infected population (ITTI), median return to normal levels of daily activity was accelerated by 2.7 days or by 27% when the patient received Oseltamivir instead of standard treatment (178.8 hours, 95% CI 156.8 to 203.2 p < .0001 for Oseltamivir 75 mg compared with 243.7 hours, 95% CI 206.5 to 276.2 for standard treatment). The greatest treatment effect was seen in the population of patients eligible for work (ITTI, full, part-time workers). In this population, median return to normal levels of daily activity was accelerated by 4.5 days, or an improvement of 41%. In this population, effects of treatment also translated into a gain in number of hours worked. Thus at day 7, the treatment effect on cumulative hours worked was between 4.716 h (95% CI 2.32, 7.11, p < .001) and 3.755 h (95% CI 0.54, 6.97, p = .022) in the 2 studies. This difference was detectable and statistically significant from day 4 of the illness onwards. CONCLUSION: The impact of influenza on the daily activities of those affected is large and should not be dismissed as trivial. Treatment with Oseltamivir has a significant beneficial effect, particularly in the working population.