Ornithine supplementation has gained popularity with athletes because of its alleged potential to release anabolic hormones, factors governing skeletal muscle hypertrophy. Three female and nine male bodybuilders served as subjects in a study to test the effectiveness of oral ornithine in bringing about the release of insulin, an anabolic hormone. After an overnight fast, subjects were administered 40, 100, or 170 mg.kg-1 L-ornithine.HCl by mouth in a random fashion on three consecutive Saturday mornings. Blood samples were drawn at baseline (T = 0), 45, and 90 min afterward. Serum ornithine levels were elevated (p < 0.01) at T = 45 and 90 min for all three dosage levels. However, serum insulin did not change from baseline levels at any dose of ornithine. The present findings show that ornithine is not an insulin secretagogue.