Continued technological improvements in the quality of nutritional formulations and techniques for parenteral administration have resulted in a major improvement in patient care. The ability to provide all necessary nutrients by intravenous infusion, so-called total parenteral nutrition (TPN), has sustained life and growth in patients who otherwise would have died. Most adult patients who derive benefit from this procedure are those with disorders in which alimentary dysfunction precludes adequate nutrition to either save life or prevent serious disease. Included among these disorders are various forms of carcinoma of the gastrointestinal tract, esophageal stricture or stenosis, intestinal fistulae, severe pancreatitis, and the “short-bowel” syndrome. Perhaps one of its advantages has been to re-establish adequate nutritional vitality to patients who suffered life-threatening malnutrition and weight loss and who, following TPN, could undergo corrective surgical procedures.The purpose of this editorial review is to discuss several interesting and sometimes preventable complications that result from the use of TPN and, in addition, to point out several situations in which TPN used too enthusiastically might directly result in death. This will not be a comprehensive review of all complications one may encounter in patients undergoing TPN. Rather, emphasis will be placed on certain electrolyte disturbances, with special emphasis on phosphate deficiency and its resulting problems. Although infection, oxalosis, disturbances of carbohydrate and lipid metabolism and the potentially important disorders related to carnitine deficiency are of critical importance in patients undergoing TPN, they will not be reviewed in this editorial.The history of TPN has amusing as well as interesting facets. About 300 years ago, Sir Christopher Wren administered a mixture of ale, opium, and beer intravenously to animals. His intravenous set was a pig bladder and his needle was a quill from a feather [1]. His work may have unintentionally represented the pioneer effort in intravenous substance abuse. More seriously, it appears that the advent of modern TPN therapy began during World War II. A fascinating review describing treatment of starvation based on sound physiological and biochemical principles appeared in 1945 [2]. Participants at this conference detailed a number of interesting observations on prisoners of war subjected to protracted starvation. They pointed out that under such conditions, the bowel underwent atrophy to the extent that it seemed to consist of only its serous coat. This was probably the derivation of the term “cellophane bowel” applied to this condition in the modern literature. Those investigators recognized clearly that under such conditions the intestine would not tolerate food administered by mouth. Almost any food acted as an irritant, causing diarrhea and dehydration. They correctly assumed and showed that administration of nutrients intravenously for several days would apparently permit sufficient functional reconstitution of the gut so that oral administration of food could be tolerated. Our current knowledge that intestinal mucosal cells can repopulate themselves very rapidly corresponds to those earlier observations.Studies conducted in 1913 by Henriques and Anderson [3] demonstrated that nitrogen equilibrium could be achieved by administering hydrolysates prepared from pancreatic extracts of goat muscle. Before the end of World War II, hydrolysates of known amino acid composition were prepared from proteins digested in proteolytic enzymes derived from pork pancreas, papain, or by simple hydrolysis in sulphuric acid [4]. It was clearly recognized at that time that the drawback of sulphuric acid hydrolysis was its destruction of tryptophane. Amino acid solutions prepared by these techniques were successfully administered to many starved people. The most successful technique appeared to be intravenous administration of protein hydrolysate preparations for 1 to 3 days followed by oral ingestion of small quantities of a solution prepared from dried milk powder, glucose, and vitamins [5, 6]. Interest in TPN was rekindled in 1968 when Dudrick, Wilmore, Vars, and Rhoads [7] showed that by this technique, normal growth and development could be maintained in children for long periods of time.