The project "Precursors of Atherosclerosis (ATS) in Children" following the protocol of WHO started in Modena in 1981/82. A total of 527 schoolchildren of 6, 9, 12 and 15, living in the area around Modena, Emilia Romagna Region, were examined, sampled from whole schools or classes. Each group exceeds the minimum of 100 children with the exception of the group including subjects of 15. The population sampled is fairly homogeneous. There are no immigrants to the area and the intra-population differences due to social-classes are minimal. The standard of life is very high: the rate of income is one of the highest in Italy and the incidence of ATS manifestations is very high. The children will be reexamined each year for three years at the same season and the study will be over in 1984. A questionnaire with family story has been filled by the parents and the parents were directly examined about: height, blood pressure, cholesterolemia, triglyceridemia, smoking habit. Following the protocol in each child are determined: height, weight, Quetelet's index (kg/m2), skinfold thickness, blood pressure, cholesterolemia, triglyceridemia, sexual maturity and smoking habit. The statistical elaboration methods of data are chosen in cooperation with the "Centro di Calcolo" of the University of Modena, and elaborated with the Statistical Package for the Social Science (SPSS) method.