In order to evaluate whether insulin-like growth factor-I (IGF-I) is associated with the development of diabetic macroangiopathy, we measured its plasma concentration in type 2 diabetics with definite myocardial infarction (MI), in type 2 diabetics without macroangiopathy (MA), and in non-diabetic healthy controls. We also compared plasma IGF-I concentration in non-diabetics with definite MI to that in non-diabetics without MA. There was a large interindividual variation in plasma IGF-I concentration in all groups of subjects studied. The median values were as follows: 0.60 IU/ml in diabetics with MI, 0.59 IU/ml in diabetics without MA, 0.48 IU/ml in non-diabetics with MI and 0.76 IU/ml in non-diabetic healthy controls. The only statistically significant difference between the groups was that between non-diabetics with MI and non-diabetics without MA. In diabetics, irrespective of MA, no significant correlation existed between plasma IGF-I level and the degree of glycemic control, renal function or various risk factors for atherosclerosis. The results of this study suggest that the high prevalence of macroangiopathy in type 2 diabetics cannot be imputed to IGF-I.