The effects on metabolism by a synthetic corticosteroid drug, clobetasone-17-butyrate, were investigated in rabbit lenses by P-31, H-1, C-13 nuclear magnetic resonance spectroscopy. No variations were observed in the levels of sorbitol, sorbitol 3-P, alpha-glycerophosphate, fructose 3-P or myoinositol. Moreover, clobetasone-17-butyrate was not shown to influence the active transport of amino acids nor to alter blood sugar levels. These results indicate that clobetasone-17-butyrate instillation does not induce side effects in the rabbit lens, as has been reported following dexamethasone treatment.