To assess whether plasma retinol-binding protein (RBP) is a marker of insulin resistance we measured RBP, insulin and glucose in 285 fasting subjects attending a Lipid Disorders Clinic as outpatients. They were grouped as either subjects without diabetes mellitus and with varying degrees of insulin resistance or subjects with diabetes mellitus according to the WHO criteria. We show that there was no association between plasma RBP and insulin-resistance, insulin, glucose, % body fat, waist circumference or BMI whether analysed together or in groups. We confirm, using the largest study cohort to date, that plasma RBP is unlikely to be a useful marker of insulin resistance.