Microvascular hyperaemia is decreased in subjects at risk of developing non-insulin-dependent diabetes mellitus (NIDDM) who have fasting hyperglycaemia. Such microvascular abnormalities may be involved in the pathogenesis of diabetic microangiopathy. To investigate the relationship of reduced microvascular hyperaemia to metabolic and blood pressure abnormalities associated with the prediabetic state, we studied 24 subjects with fasting hyperglycaemia and 24 age- and sex-matched control subjects. The microvascular hyperaemic response to local heating of the skin on the dorsum of the foot measured by laser Doppler fluximetry was reduced in the subjects with fasting hyperglycaemia (1.18 [0.87-1.83] volts vs 1.51 [1.30-2.14] volts normal subjects; p = 0.0002) and was negatively correlated with fasting plasma insulin concentration (Rs = 0.70; p = 0.001) and positively related to insulin sensitivity determined by continuous infusion of glucose with model assessment (CIGMA) (Rs = 0.52; p = 0.01), but showed no association with fasting plasma glucose, beta-cell function 24 h ambulatory blood pressure profiles or serum lipid concentrations. These results suggests that hyperinsulinaemia, as a result of insulin resistance, may have a detrimental effect on microvascular function in the prediabetic state.