The main aim of this study was to examine changes in relative weight and prevalence of obesity across a ten-year period among 14-year-old boys according to parental education level. Data from two surveys, carried out in 1987 and 1997, of boys attending the 7th grade of primary schools in Wrocław were used in the analysis. The heights and weights of 3165 boys aged 14 years selected from cohort of 6969 7th and 8th grade boys from all primary schools of the city Wrocław were used. The data of the second sample of 14-year-old boys (n = 1014) were obtained from a health examination study carried out in the Silesian Centre for Preventive Medicine, 'DOLMED', in Wrocław in 1997. All boys attended the 7th grade of 34 randomly selected primary schools from a total of 129 schools in the city of Wrocław. Social status was assessed on the basis of parental education level scored to four categories: university, secondary school, trade school, and elementary school. The prevalence of overweight and obesity was defined as the percentage of children above the 85th and 95th percentiles of the body mass index (BMI), the means of which were 21.27 and 23.75 kg/m2 respectively. Prevalence of overweight among boys is slightly lower in the 1997 sample, whereas the prevalence of obesity shows the opposite trend and is higher by more than one percent in comparison with the 1987 sample. Similar trends of declining medians and increasing variance are observed in all educational groups. The differences in medians between the two samples within educational groups did not achieve statistical significance for the groups with parents with education at elementary level and fathers with university education. There is a trend toward increasing prevalence of obesity across the decade considered, according to father's education level. With respect to mother's education levels, the most dramatic changes in BMI and obesity occurred in the elementary education group, where the percentage of obese subjects increased more than twofold. A significant increase is also observed in the group with parents attaining university education.