The YAG laser is being used more often in cases of nonresectable bronchogenic cancer and in some cases is called on in lieu of surgery for tracheal stenosis. Patient safety hinges first on the endoscopist's technical skill and second on his understanding of the dangers involved in laser therapy. This report is based on experience gleaned from a 1,503 case series of endoscopic YAG laser treatments on 839 patients. These treatments were carried out by seven endoscopists in four teams using exactly the same equipment and techniques. In spite of the use of this high-risk technique in a high-risk patient population comprising a majority of major airways malignancy, the mortality rate was only 0.4 percent (six deaths: all in the postoperative period). We attribute this success to careful screening prior to resection, whenever possible, and above all to our methodology which not only emphasizes prevention but also enables rapid response.