Photodynamic therapy (PDT) for cancer in the esophagus and bronchi with red (630 nm) light may occasionally lead to wall perforation and fistula. Therefore, the clin. use of a less penetrating wavelength (514 nm) was investigated for the curative treatment of nine superficial carcinomas in the esophagus and bronchi after photosensitization with Photofrin II. Tumors without infiltration beyond the submucosa in the esophagus and beyond the lamina propria in the bronchi were considered as superficial cancers. The outcome and complications were compared with those of 13 superficial cancers treated with PDT and 630 nm light. In addn., we evaluated histol. the extent of the long-term tissue damage and scarring following treatment of six esophageal cancers with either green or red light. At first endoscopic control, 7-10 days after PDT, tissue necrosis simply matched the illuminated area, without evidence of selective tumor damage. Six of nine tumors treated with 514 nm light had a complete response compared with nine of 13 after 630 nm irradn. No perforation or fistula occurred in either treatment group. However, severe chest pain and fever with or without pleural effusion, consistent with occult perforation, were obsd. in three patients after 630 nm illumination in the esophagus. Histol., fibrous scarring in the three distinct sites treated with green light was limited to the superficial layers of the esophagus. After red light treatment, transmural fibrosis with marked thinning of the esophageal wall was evident in two of the three specimens available for inspection. These results indicate that PDT with 514 nm light has the potential to cure superficial cancer in the esophagus and bronchi with essentially the same probability of success as red light. In the esophagus, green light prevents deep tissue damage, thus reducing the risk of perforation.