A prospective randomized trial was conducted comparing the addition of iv hyperalimentation (IVH) to Corynebacterium parvum, isophosphamide, and adriamycin (CIA) chemoimmunotherapy in 26 patients with extensive squamous cell lung cancer. Thirteen patients were entered in each treatment arm of the study and IVH was administered before and after the first course of CIA for a total of 31 days. The major dose-limiting toxic effect of CIA was leukopenia. Less myelosuppression was observed for the patients receiving IVH. The difference in the lowest recorded leukocyte and neutrophil counts between the two groups was significant (P = 0.03 and 0.01, respectively). Also, a significant decrease (P = 0.06) in nausea and vomiting associated with chemotherapy administration was found for the IVH gorup. The differences in toxic effects between each group were not maintained over subsequent courses of therapy when both groups received CIA alone. The prevention of the toxic effects of chemotherapy by IVH suggests a means of giving higher chemotherapy doses with the intent of increasing tumor response and patient survival.