From July 1984 through March 1987 23 patients with small cell lung cancer have entered a trial at the University of Pennsylvania. Concurrent Platinum (DDP) Etoposide (VP-16) chemotherapy and twice-daily, 150 cGy radiotherapy to a total dose of 4500 cGy in 3 weeks was used. Besides the twice-daily radiotherapy, multiple field arrangements attempted to minimize normal tissue exposure while concentrating on the target volume. Sophisticated CT-assisted treatment planning employing beams-eye-view technology was used. Esophagitis occurred in 73% (13% severe); hematologic toxicity occurred in 65% (17% WBC less than 1000). Response--100% in pure small cell carcinoma, 91% overall. Median follow-up is 22 months with an actuarial projection of 56% 2-year survival. Median survival is not yet reached. This is a highly effective therapy with substantive but tolerable toxicity. Accrual and follow-up continues. This is a preliminary report. We expect 30 patients before closing the study. A parallel study is underway in the Eastern Cooperative Oncology Group, with a randomized prospective trial in the design stage.