Radiation therapy may induce anorexia with resultant weight loss and inanition that can limit the dose of radiation therapy administered. The purpose of this study was to evaluate 39 nutritionally-depleted patients who had a variety of malignant diseases treated with radiation therapy and concomitant nutritional support with intravenous hyperalimentation (IVH). The average dose of radiation delivered was 3827 rads in an average of 3.5 weeks. Ninety-five percent of the patients completed their planned course of radiation therapy and improved symptomatically. Fifty-four percent of the patients responded with a greater than 50% reduction in tumor size. Responding patients gained an average weight of 13.0 +/- 6.5 lbs. during IVH (av. 36.2 days) and radiation therapy (av. 3832 rads), whereas non-responding patients gained only 4.9 +/- 8.8 lbs. (p less than 0.001) during IVH (av. 42.8 days) and radiation therapy (av. 3819 rads). Serum albumin concentrations rose from 3.12 +/- 0.49 gm/100 ml to 3.51 +/- 0.68 gm/100 ml (p less than 0.05) during treatment in responding patients but did not rise significantly from 3.09 +/- 0.48 gm/100 ml in non-responding patients. In conclusion, IVH allowed a planned course of radiation therapy to be delivered to a group of poor-risk, malnourished cancer patients, and a positive correlation between tumor response and nutritional status was identified. Moreover, IVH was a valuable adjunct in the treatment of six patients who had enteric fistulas that originated from radiated bowel.