Exercise should be an integral part of the treatment in non-insulin-dependent (NIDDM) diabetic patients, yet most of these patients' performance is low, mainly because of their obesity and concomitant macrovascular disease. We studied the influence of a moderate exercise training on parameters of glucose control in NIDDM patients. Forty patients aged 56.6 +/- 6.6 years were assigned randomly according to age and sex into exercise and control groups. The exercise group trained for 45 min 3 times weekly for 12 weeks, while the control group did not change their lifestyle. At the end of the study the exercise group had a significant reduction in plasma levels of triglycerides, fructosamine and glycohemoglobin. The improvement in metabolic control persisted significantly in patients who continued to exercise at varying levels at home during 1 year of follow-up.