Diabetes Intervention Study. Multi-intervention trial in newly diagnosed NIDDM. OBJECTIVE: In a randomized 5-yr multi-intervention trial, we tested the efficacy of intensified health education (IHE) in improving metabolic control and reducing the level of coronary risk factors and incidence of ischemic heart disease (IHD). RESEARCH DESIGN AND METHODS: Within the intervention group, the benefit of clofibric acid was evaluated in a double-blind study. One thousand one hundred thirty-nine newly diagnosed middle-aged (30- to 55-yr-old) patients with non-insulin-dependent diabetes mellitus (NIDDM) entered the study. They were classified as diet controlled after a 6-wk screening phase with conventional dietary treatment. During the follow-up, the control group (n = 378) was cared for at different diabetes outpatient clinics with a standardized surveillance. The intervention group (n = 761) had a structured IHE that included dietary advice, antismoking and antialcohol education, and ways to enhance physical activity. RESULTS: Randomly, 379 of the IHE patients received 1.6 g clofibric acid/day, and the others received placebo. IHE resulted in improved glucose control (adjusted fasting blood glucose) levels after 5 yr (control subjects 9.27 mM, IHE group 8.71 mM, and IHE plus clofibric acid group 8.60 mM, P less than 0.01). The better glycemic control was achieved with fewer antidiabetic drugs. After 5 yr, antidiabetic drugs were prescribed to 47% of the control subjects, 28% of the IHE group, and 34% of the IHE plus clofibric acid group (cutoff limit for drug application was postprandial blood glucose of greater than or equal to 13.87 mM). The ratio of polyunsaturated to saturated fatty acids (0.26 vs. 0.40, P less than 0.01) and physical activity (174 vs. 327 scores, P less than 0.01) were increased, and blood pressure, tobacco, and alcohol consumption were significantly reduced by IHE. However, IHE had no effect on calorie intake, percentage of fat in the diet (45%), and body weight. The most important finding was the significant increase of blood cholesterol in all three groups (+0.47, +0.36, and +0.34 mM, respectively). Clofibric acid only prevented the increase of triglyceride levels (+0.56, +0.24, and +0.05 mM, respectively). The incidence rate per 1000 for myocardial infarction was 30.3 for control subjects, 53.6 for the IHE group, and 55.6 for the IHE plus clofibric acid group. The corresponding rates for IHD incidence were 90.9, 97.8, and 98.8, respectively. Men suffered more frequently from myocardial infarction, whereas women developed ECG criteria for IHD more frequently. Among the 35 cases of death, besides cardiovascular diseases, liver cirrhosis and neoplasia were the predominant causes. The death rate per 1000 in control subjects was 46.2, 30.6 in the IHE group, and 27 among patients with IHE plus clofibric acid. CONCLUSIONS: IHE was of substantial benefit for the control of glycemia, significantly diminished the need for antidiabetic drugs, and reduced a cluster of risk factors but had no effect on the control of blood lipids. This could be one major reason for the failure of IHE, effective lowering of blood pressure, and clofibric acid to prevent cardiovascular complications. Clofibric acid was only effective in reducing triglycerides.