A simple and rapid microassay for the titration of human respiratory syncytial virus. 
A microassay, using tissue culture microplates for the titration of human respiratory syncytial virus by syncytium formation, is described.  Virus titers obtained agreed well with those obtained in a larger assay system; the microassay, however, is more rapid and economical.  Large numbers of virus samples are easily and rapidly processed as the assay necessitates an incubation period of only three days.