A German shepherd dog, male, seven-month-old, with gastric dilatation was examined clinicopathologically and radiographically. X-ray findings showed radiopaque linear materials, which were identified a number of pieces of commercial antiparasitic collar, $Preventic^{circledR}$(Amitraz, Virbac) by gastrotomy. The dog became good a day after removal of the materials in the stomach. It was considered that the gastric dilatation was caused by rapid absorption of the amitraz which could induce paralysis of stomach.