SUMMARYFew studies have examined the relationship between viral activity and bacterial invasive disease, considering both influenza virus and respiratory syncytial virus (RSV). This study aimed to assess the potential relationship between invasive pneumococcal disease (IPD), meningococcal disease (MD), and influenza virus and RSV activity in The Netherlands. Correlations were determined between population-based data on IPD and MD during 1997-2003 and influenza virus and RSV surveillance data. Incidence rate ratios of disease during periods of high influenza virus and RSV activity over the peri-seasonal and summer baseline periods were calculated. The analyses comprised 7266 and 3072 cases of IPD and MD. When data from all seasons were included, the occurrence of pneumococcal bacteraemia and MD correlated significantly with influenza virus and RSV activity both in children and adults. Periods of increased influenza virus and RSV activity showed higher rates of pneumococcal bacteraemia in older children and adults than the peri-season period. Rates of MD in children were also higher during periods of increased influenza virus activity; the same appeared true for MD in older children during periods of increased RSV activity. Although no causal relationship may be inferred from these data, they support a role for influenza virus and RSV in the pathogenesis of IPD and MD.