PURPOSE: To evaluate pathologic changes of the trachea and the lung after insertion of silicone covered and non-covered Gianturco stent in the trachea of dog. MATERIALS AND METHODS: Silicone covered(covered) and non-covered(bare) Gianturco stents, six in each, were inserted into the tracheal lumen of six consecutive dogs. After 1--10 week observation, the dogs were sacrificed and their tracheas and lungs were examined grossly and histopathologically. Serial chest radiographs were performed to evaluate pneumonia and stent migration every 3--5 days. RESULTS: Pneumonia was observed in one of bare stent group and five of covered stent group. Stent migration was noted in three of covered stent group. In bare stent group, the epithelium of the trachea was markedly thickened by hyperplasia and stent was covered by granulation tissue from 6 weeks after stent insertion. Inflammation was focal at contact site between the stent and the trachea. In covered stent group, the epithelium was denuded at multiple areas and there were multifocal squamous metaplasia of the mucosa. Inflammatory reaction of the trachea was diffuse. CONCLUSION: Inflammatory reaction was more severe and stent migration was more frequent in covered stent group. The use of covered stent in the trachea should be studied further.