To evaluate the influence of blood glucose control on serum catecholamine levels (which reflect both plasma and platelet levels), six healthy non-diabetic subjects, seven well-controlled Type 1 diabetic patients, and six poorly controlled Type 1 diabetic patients were studied before (baseline) and after standardized exercise. A significant correlation was found between serum noradrenaline and HbA1 at baseline (r = 0.53, p less than 0.025) and after exercise (r = 0.71, p less than 0.001). Similar results were found for serum adrenaline (r = 0.68, p less than 0.005 and r = 0.61, p less than 0.005, respectively) and consequently total serum catecholamine content (r = 0.65, p less than 0.005 and r = 0.75, p less than 0.001, respectively). However, no relationship was found between serum catecholamine levels and actual blood glucose levels, age, body mass index or insulin dose. A moderate correlation was found between systolic blood pressure and serum levels of noradrenaline and total catecholamines after exercise (r = 0.48 and r = 0.48, both p less than 0.025).