Insulin binding on circulating red cells has been studied in hypertriglyceridemic (HTG) patients before and after normalization of plasma TG levels by a low fat and low CHO diet, followed for 2 months. Under basal condition HTG patients showed lower insulin binding on red cells (B/T) than control subjects. The reduction in binding was due to a lower receptor number (binding capacity). After the diet and normalization of TG levels, insulin binding was identical in HTG patients and always lower than in controls. The fasting values of blood glucose, IRI, FFA, were also unchanged after TG reduction, suggesting, together with the low insulin binding, a state of insulin resistance. We conclude that our lean patients, affected by HTG, present a state of insulin resistance. Despite normalization of plasma TG, obtained with diet alone, insulin receptor binding on red cells in unchanged.