The present report confirms the anti-hyperglycaemic and anti-dyslipidemic properties of 4-hydroxyisoleucine, an unusual amino acid isolated from Trigonella foenum-graecum seeds, for the first time in a well-characterised model of type II diabetes, i.e. db/db mice. 4-Hydroxyisoleucine, when given orally to these mice at 50 mg kg(-1) dose level, significantly (p < 0.05) declined their elevated blood glucose, plasma insulin, triglycerides, total cholesterol, low-density lipoprotein-cholesterol levels and raised their declined plasma high-density lipoprotein-cholesterol level. These results indicate that 4-hydroxyisoleucine exhibits significant potential as an anti-diabetic agent by suppressing progression of type II diabetic states that is suggested by enhancement of insulin sensitivity and glucose uptake in peripheral tissue.