Photodynamic therapy (PDT) is a surface oriented, locally cytotoxic intervention being investigated for oncologic therapy. Surfaces such as the pleura or the peritoneum are frequently involved with primary or metastatic cancer, and the chance for cure in such situations is low due to the inability to eradicate all the disease. A series of investigations have been performed at the National Cancer Institute since 1985 studying the possible use of PDT for large cavity treatment. This report details evolution of the methodology, toxicity, and overall feasibility of the delivery of intrapleural PDT to patients after debulking of primary and malignant chest neoplasms, with an emphasis on malignant pleural mesothelioma. These investigations have culminated in an ongoing Phase III trial to define the efficacy of intrapleural PDT.