OBJECTIVE: To determine whether arginine supplementation affects tumor growth or metastases in well-fed and starved mice using a squamous cell carcinoma VII tumor model. DESIGN: Prospective study in a murine model. INTERVENTIONS: Simulation of the cachectic state often seen in patients with head and neck cancer, induction of squamous cell carcinoma, and administration of standard and arginine-supplemented diet. MAIN OUTCOME MEASURES: Effect of arginine supplementation on tumor growth, metastases, and host weight gain. RESULTS: Tumor weight was significantly decreased in those animals receiving 5% arginine supplementation. The rate of metastases was lower in animals receiving arginine, but this difference did not reach statistical significance. All groups receiving supplemental arginine experienced weight loss, which contradicts the findings that arginine as an anabolic agent may not be present in cancer-bearing hosts.