BACKGROUND Impaired ability to eliminate lipids in the postprandial state is an atherogenic trait associated with insulin resistance. OBJECTIVE To assess insulin sensitivity and postprandial triglyceride metabolism in prediabetic persons. METHODS Cross-sectional study. METHODS Sahlgrenska University Hospital, Göteborg, Sweden. METHODS 13 healthy, normotriglyceridemic men with two first-degree relatives with type 2 diabetes and 13 carefully matched controls without known diabetes heredity. METHODS Oral glucose tolerance test, insulin sensitivity (euglycemic clamp technique), and fasting and postprandial triglyceride levels after a mixed meal. RESULTS Relatives of persons with type 2 diabetes were insulin resistant but had normal glucose tolerance. They exhibited postprandial hypertriglyceridemia; the 6-hour triglyceride incremental area under the curve was 50% higher than that of the control group (P = 0.037). CONCLUSIONS These healthy male first-degree relatives of patients with type 2 diabetes are insulin resistant and exhibit postprandial lipid intolerance despite having normal fasting triglyceride levels. These characteristics, which occur in the absence of glucose intolerance, are associated with an increased risk for macroangiopathy.