In 52 both sex obese children (mean age was 9.7 +/- 2.5), blood pressure and biochemistry parameters in blood were studied after controlled hypocaloric diet. The data, collected in two out patient visits in intervals of one year and half and four years, were: blood pressure; total, HDL and LDL cholesterol; apoproteins A1 and B; NEFA; triglycerides; phospholipids; haematocrit; haemoglobin; glycosylated haemoglobins A1 and A1C; glucose; insulin; seric proteins: fibrinogen; platelets; Quick time and activated partial thromboplastin time. The group of obese children with a successful response to the hypocaloric diet treatment (significant loss of weight) showed a decrease in the plasmatic levels of Apoproteins A1 and B, triglycerides, NEFA and insulin together with an increase in the level of HDL cholesterol. These changes weren't so significant in the group of obese children who didn't lose weight. When we took into account plasmatic cholesterol, the obese patients with normal plasmatic level of cholesterol showed a significant descend in the risk factors. However, in the obese children with high cholesterol despite the dietetic treatment, the pathologic plasmatic profile didn't show any change. Finally, while the group with maintained high level of insulin showed a significant increase of apoproteins A1 and B, and total and HDL cholesterol, the group where the insulin levels became normal after treatment showed a good development of the biochemistry parameters studied. The fibrinogen level and blood precision which remained high in both visits were studied taking into account age and growth pattern.