Altogether 86 patients with recently diagnosed NIDDM, aged 40-64 years were randomised after 3 months of basic education to intensified diet (Int. group, 21 men, 19 women) or conventional treatment groups (Conv. group, 28 men, 18 women). The aim was to examine whether an intensified diet education would result in a better metabolic control and greater reduction in cardiovascular risk factors than conventional treatment for obese patients with recently diagnosed type 2 diabetes mellitus. Furthermore, both groups were re-examined after a second year of observation period to find out the maintenance of the results after intervention. After basic education, Int. group participated in 12-months diet education, while Conv. group was treated in local health centres. During the intervention period, only Int. group showed further weight reduction. Only 20% of patients in Int. and 6% of patients in Conv. group had BMI < 27 kg/m2 at the end of the intervention, while 75% of patients in Int. and 52% of patients in Conv. group had achieved a good metabolic control (fasting blood glucose < 6.7 mmol/l; P = 0.005 between groups). Serum total cholesterol did not change significantly, but the changes in HDL-cholesterol, triglycerides and apolipoprotein B level were significant in Int. group only. The proposed acceptable values for serum lipids were achieved by 52 to 88% of patients without major differences between the two groups. During the second year of observation, weight gained in both groups and a deterioration was seen in metabolic control. Despite that a greater proportion of patients in the Int. group still was in good metabolic control (55.3% vs. 31.8%, P = 0.016), furthermore Int. group was receiving less frequently oral drugs for hyperglycaemia than Conv. group. No differences in serum lipids were observed between the groups after the observation period. HDL-cholesterol showed a persistent improvement in both groups.