An outbreak of influenza-like disease caused illness among 48 per cent of 173 female military recruits, 35 per cent of whom smoked cigarettes. The risk of influenza-like illness was greater in smokers (60.0 per cent) than in nonsmokers (41.6 per cent), with a risk ratio of 1.44 (95 per cent CL 1.03-2.01). Among those ill, a significantly greater proportion of smokers visited the clinic than nonsmokers. This could have been due to more severe illness among smokers, or to a greater tendency to visit the physician. The proportion of influenza-like disease attributable to smoking in this population was 13 per cent.