['Insulin resistance in patients is associated with increased atherosclerosis and arterial restenosis. It is thought that the concomitant hyperinsulinaemia exacerbates vascular disease because resistance to insulin-induced glucose disposal is associated with resistance to certain effects of insulin which inhibit, but with no resistance to other effects which promote, neointimal hyperplasia. We sought to determine the net effect of hyperinsulinaemia on neointimal hyperplasia in normal animals.', 'Rats were infused with or without insulin for 16 days and the carotid artery injured by balloon catheter on day 2.', 'Steady-state serum insulin concentrations were 0.56 +/- 0.04 and 1.25 +/- 0.05 nm for control and hyperinsulinaemic rats respectively (p < 0.01). Systolic blood pressures, weights and serum glucose levels were not affected by hyperinsulinaemia. Fourteen days after injury, the neointima-to-media area ratio was 0.72 +/- 0.07 and 1.39 +/- 0.15 for control and hyperinsulinaemic rats respectively (p < 0.05). Media area was unaffected by hyperinsulinaemia.'] Does insulin stimulate arterial neointima formation in normal rats after balloon injury?