The effects of short-term acute nutritional deprivation and refeeding on immune function was investigated in rats. Animals previously sensitized to keyhole-limpet hemocyanin were starved for 72 hours and refed for 7 days. Recall skin testing with keyhole-limpet hemocyanin and immunization with tetanus toxoid (TT) were used to assess delayed-type hypersensitivity (DTH) and humoral immune responses. DTH was maximally depressed late, after refeeding had begun. Anti-TT responses were depressed early during starvation. Neither DTH nor anti-TT responses had returned to normal after a period of refeeding sufficient to restore weight. The data indicate that short-term acute nutritional deprivation may contribute to acquired immunodeficiency in patients undergoing surgery.