Over the past twenty five years the development of total parenteral nutrition has in many ways revolutionised the practice of surgery. It has enhanced survival in otherwise high mortality operations such as oesophageal surgery, especially with anastomotic complications. It has changed significantly the management of fistulae, either post operative or associated with diseases such as Crohn's enteritis. Here a basic general principle is applied--that a fistula will close if there is no distal obstruction and the throughput can be diminished. This can be achieved by withholding oral feeding and using the parenteral route. It has allowed survival in the short gut syndrome from whatever cause and it is interesting to see the degree of "intestinal adaptation" that occurs once the first critical year is survived with the help of intravenous nutrition. The assessment of nutritional status is difficult and while the level of serum albumin may be taken as a clinical standard, it is obvious that many patients survive extensive surgery with low albumin levels and also that there appears to be a lag period to the restoration of albumin levels, even with otherwise successful nutritional support and with other parameters being satisfactory. Even complex formulae using a combination of laboratory and antropometric parameters is not fully satisfactory as an absolute assessment of nutritional status. It is now interesting to see that nutrition can affect both immune competence and even carcinogenesis. The lipid element in intravenous nutrition may cause dysfunction of immunity and vitamin status, gastric and platelet function with impaired oxygen diffusion leading to increased wedge pressures.(ABSTRACT TRUNCATED AT 250 WORDS)