Diarrheal stools of an acute porcine gastroenteritis were examied by electron microscopy and inoculation into cell cultures. Two types of virus, coronavirus-like and calicivirus-like, were detected by direct electron microscopy, and cytopathogenic astrovirus-like virus was isolated in ESK cell cultures. This is the first report on the detection of calicivirus- and astrovirus-like viruses in porcine diarrhea in Japan, and on the isolation of cytopatogenic astrovirus-like virus in cell cultures.