The matrix protein of paramyxoviruses plays an important role in virus assembly through its interactions with cell membrane, virus envelope and virus nucleocapsid. In the present study, we investigated the possible association of respiratory syncytial virus (RSV) matrix (M) protein with the plasma membrane of infected cells. Using confocal microscopy we found that M was present at the cytoplasmic side of the plasma membrane. We used flotation gradients to purify membranes from RSV infected cells and treated them with cold Triton X-100 to obtain lipid rafts in the insoluble fraction. Western blot of the lipid raft fraction with specific antibodies showed that it contained M, as well as G (attachment) and N (nucleocapsid) proteins. We also found that RSV purified on sucrose gradients contained lipid raft markers. Together, our data suggest that RSV uses lipid rafts for assembly and budding.