OBJECTIVE Respiratory infections require a rapid etiological diagnosis for efficient management of cases. We evaluated multiplex PCR used for the diagnosis and the epidemiological surveillance of influenza and respiratory syncytial virus (RSV) infections. METHODS Our study included 278 patients (mean age: 37.2+/-22.9 years) with flu or flu-like syndromes, consulting physicians affiliated with the GROG Poitou-Charentes or hospitalized in the Poitiers teaching hospital. A multiplex PCR detecting A(H3), A(H1) and B influenza viruses, and RSV A and B, was performed with both a direct examination by immunofluorescence and cell-culture. RESULTS We diagnosed a viral infection in 139 (50.0%) patients: 99 cases of influenza A(H3), 2 cases of influenza A(H1), 28 cases of influenza B and 11 cases of RSV infections. The diagnosis yield in GROG patients (52.3%) was significantly higher than that observed in hospitalized patients (34.5%) (P=0.04). All techniques were correlated in 61% of cases. The multiplex PCR yielded 22.3% more positive samples compared to the conventional techniques. All positive samples by conventional techniques were also positive by multiplex PCR. We observed a perfect correlation between viral types and subtypes determined by PCR and cell-culture. CONCLUSIONS Multiplex PCR is a sensitive technique allowing an efficient and rapid diagnosis of respiratory infections due to influenza and RSV.