A disease syndrome of broiler chickens is described. Affected birds exhibited poor pigmentation of the shanks, decreased weight gains, elevated feed conversions, poor feathering, enlargement of the proventriculus, and a decrease in the size of the gizzard. Reoviruses were isolated from affected chickens from several farms. Signs and lesions similar to those seen in chickens with the field syndrome were reproduced when these isolates were inoculated into day-old chicks with low levels of maternal antibody against viral arthritis. The pathogenicity of the viral isolates was variable. The incidence of lameness was much higher in those groups of chicks injected with these viruses than in the control groups.