Delivery of total parenteral nutrition (TPN) is a complex procedure requiring a basic knowledge of nutritional physiology and an understanding of the impact of various disease states on utilization of nutrient substrates. The goals of TPN are to reverse catabolism, promote anabolism, and build structural protein. It is important to infuse an adequate amount of calories and protein but to avoid the stress of overfeeding. Various laboratory values may be monitored to ensure that each of the nutrients administered is being adequately tolerated by the patient. Keeping these principles in mind, primary care physicians can deliver a TPN regimen specifically suited for individual patients and can anticipate and prevent any potential complications.