Equipment, techniques, and solutions have been developed for the chronic intravenous feeding of rats. With use of a special harness and fluid infusion swivel assembly, 140- to 250-gm, unrestrained rats can be fed for weeks at a time exclusively by vein, allowing for prolonged periods of metabolic and nutritional study. A 32% dextrose and 5% amino acid solution containing essential minerals and vitamins was formulated for the intravenous feeding regimen. This model can be readily utilized and has great potential value for studying problems related to surgical nutrition and metabolism.