Continuous, hyperfractionated, accelerated radiotherapy (CHART) has been used at the Mount Vernon Cancer Treatment Center since January 1985. Patients with head and neck tumors and those with locally advanced non-oat cell carcinoma of the bronchus have formed the large majority of the 263 patients treated. Early reactions in the mucosae of the mouth and pharynx have been pronounced, but all have healed, while those in the skin have been less severe than with conventional radiotherapy. An unexpected late morbidity was radiation myelitis in four patients, but in other tissues including the skin, mucosae, the connective tissues, and the salivary glands, late changes appear reduced compared to those after conventional radiotherapy. In 92 patients with squamous cell carcinoma of the major sites in the head and neck region, of whom 71 were in Stages T3 and T4, a complete regression at the primary site and nodes was achieved in 90%. This can be compared with 62% in similar patients previously treated with curative intent at Mount Vernon between 1980 and 1985; the difference was maintained in follow-up (p = 0.003). Of 76 assessable patients with non-oat cell carcinoma of the bronchus, a complete radiological response has been achieved in 40%, compared to 12% in a retrospective group; again the difference has been maintained in follow up (p = 0.0001). A 1-year survival of 60% can be compared to 40% in the retrospective group and a 2-year survival of 29% compared to 12% (p = 0.01). With a reduction of permitted dose to the spinal cord, CHART gives promise for improvement in tumor control and a reduction in late morbidity. These promising results have led to multi-center randomized controlled clinical trials in carcinoma at the head and neck and in non-oat cell carcinoma of the bronchus. In these studies, CHART is being compared with conventional fractionated radiotherapy.