There have been many recommendations regarding trace element needs of adults receiving total parenteral nutrition. Balance studies for zinc, copper, manganese, chromium, selenium, and molybdenum were carried out in 3 critically ill patients in an intensive care unit. Results indicate that the need for zinc was great in them, but that for copper and manganese was lower. Small negative chromium and selenium balances were observed. Molybdenum, iron, cobalt, and iodine balances were attempted but proved difficult to interpret. The requirement of each trace element varied from patient to patient, and was influenced by the presence of gastrointestinal fluid loss and renal function.