The possibility of intraperitoneal (IP) parenteral nutrition was suggested after the observation that glucose and amino acids pass from the peritoneal cavity into the systemic circulation. We used rabbits to study the characteristics of the transfer of glucose, lipids and amino acids. An IP injection of glucose 25% (1 g/kg) produced a peak level in the serum within 40 min. A 20% fat solution (1 g/kg) showed maximum serum levels of triglycerides and total lipid in 2.5 h, while a standard amino acid solution (1.5 g/kg) enriched with 25 14C-phenylalanine peaked serum levels in 16 min. The 4 rabbits survived for 28 days with IP glucose, amino acids and lipids as the only form of nutrition, apart from water. When sacrificed after 28 days histology of peritoneum, liver, spleen, gut and kidney showed no abnormality. We conclude that the basic nutritional components are adequately absorbed through the peritoneum, and that long-term nutritional support can be achieved uneventfully with IP administration of nutritional solutions.