The movement of a single dose of 14C-putrescine in the lumen of the rat gastrointestinal tract was followed for 3 hours after intragastric intubation. Putrescine progressed in the gut lumen in a wave-like fashion and was absorbed in the small bowel. Maximal uptake was observed at 2 hours; therefore, this time-point was selected to measure the concentration dependency of putrescine uptake by the small intestine and distribution between the vital organs in a wide concentration range (1/10 to 100 times the dietary input). Putrescine uptake by the small bowel was likely to be by passive diffusion, because the absorption was in proportion to input. The fate of putrescine was determined in the plasma, small bowel, liver, and skeletal muscle by measuring the radioactivity of the polyamines, their acetyl derivatives, and amino acids at physiologic concentrations. It appears that approximately 10% of the dietary input reaches the putrescine body pool.