To compare the safety and efficacy of PDT plus XRT versus XRT alone in patients with obstructive endobronchial tumors, 41 patients with inoperable non-small cell bronchogenic carcinoma obstructing a central airway were randomized into either XRT alone or PDT followed by XRT. The most proximal site of obstruction was in a main stem bronchus (32) or a lobar bronchus (9). The histology was squamous cell carcinoma in 34, large cell carcinoma in 4, and adenocarcinoma in 3. The age, location of tumor, degree of endobronchial obstruction, and Karnofsky rating were similar between the two groups. The radiation dose was 3000 cGy in 10 fractions over two weeks using a parallel pair technique. The patients were reassessed 4, 8, and 12 weeks after completion of XRT and then quarterly thereafter. Response to treatment was assessed by changes in respiratory symptoms, bronchoscopy, spirometric measurements and arterial blood gas sampling. All 20 patients improved symptomatically after PDT and XRT. Four out of 21 patients failed to respond after XRT alone. The median interval between treatment and local recurrence was two times longer in the PDT and XRT group (233 days versus 107 days, p equals 0.005). Our results suggest that the addition of PDT prior to XRT provides significantly better and longer lasting local control than XRT alone.