OUTLINE: This is a noncomparative study. PDT consists of IV porfimer sodium followed 40-50 hours later by laser red light delivered by optic fibers passed through the biopsy channel of an endoscope. Retreatment, if necessary, consists of up to 3 injections at least 30 days apart and up to 6 laser light treatments, with a maximum of 2 following each injection. Patients are followed monthly for 4 months, and then periodically for at least 5 years.