The pathogenicity of the G-4260 strain of picornavirus for day-old chicks was studied by intraperitoneal inoculation. No clinical signs were observed. A mild yellowish-tan discoloration of the kidneys was noticed in necropsy 7 to 21 days after inoculation. Mean body weight was significantly lower (P less than 0.01) in inoculated groups than in control groups 7 days after inoculation. In a chronological study on the distribution of the virus in organs, the virus was recovered from various organs, exclusive of the brain and trachea. The virus titer was higher in the kidneys, jejunum, rectum, and bursa of Fabricius than in any other organ. Fluorescent antigens were seen predominantly in the epithelia of the renal tubules.