Epidemic gastroenteritis was transmitted to human volunteers by the oral administration of fecal filtrates. The original inocula were obtained from patients in a natural outbreak which occurred at Marcy State Hospital in the winter of 1946–47. The experimental disease closely resembled that of the donors. The incubation period ranged from I to 5 days, with a mean of 3 days. The disease was carried through three generations, in the last two by means of fecal filtrates. Oral administration of unfiltered throat washings from experimental cases of the disease likewise induced gastroenteritis but subjects who inhaled a portion of the same throat washings remained asymptomatic. Volunteers who inhaled throat washings taken from patients in the epidemic at Marcy State Hospital also failed to develop the disease. Five volunteers who had previously been inoculated with fecal filtrates were reinoculated with the same material. Gastroenteritis followed in one of the two subjects who had failed to contract the disease the first time. The others remained well. Embryonated hens' eggs were inoculated with one of the two unfiltered stool suspensions used in the pool which had induced gastroenteritis in each of the three volunteers to whom it was fed. Three sets of eggs were inoculated: one on the chorioallantoic membrane, another into the yolk sac, and a third into the amniotic sac. Three serial passages were carried out by each method at varying time intervals. Penicillin and streptomycin were employed as antibacterial agents. Tissue and extraembryonic fluids from the third passage were non-infective for volunteers.