Study aim: To assess the size of secular trends in the physical fitness of boys from eastern Poland taking into consideration stages of education. Material and methods: The physical fitness results of boys aged 7-19 years living in eastern regions of Poland were analyzed: 3188 students were examined in 1986 while in 2006 the research included 10 810 boys. In both examinations (1986 and 2006), the level of motor abilities was measured according to the guidelines of the International Physical Fitness Test. The individual results of children and youth examined in 2006, which took into account calendar age, were converted into points on a T scale, with means and standard deviations from 1986 accepted as norms. On the basis of the obtained point values and taking into account stages of education (7-9--integrated teaching, 10-12--primary school, 13-15--lower-secondary school, 16-18--upper-secondary school), arithmetic means and dispersion values concerning motor abilities in the groups were calculated. Individual results in motor abilities of every subject were used to define quantitative generation changes. Differences between the means obtained in 1986 and 2006, as well as between the fractions of boys qualified for respective fitness category in both examinations, were assessed. Results: Over the 2-decade period the boys from eastern Poland slightly improved their results only as far as sit-ups are concerned (1.47 points), while the level of bent arm hang, handgrip, 50 m run, and shuttle run 4x10 m remained the same. In contrast, negative changes were observed in the long run (4.44 points), the sit-and-reach test (4.47 points), and the standing broad jump (3.74 points). The greatest decline in motor abilities was noted amongst schoolchildren from integrated education classes (2.69 points); whereas the smallest decline was noted in adolescents from lower secondary schools (0.60 points). Conclusions: The changes noted in physical fitness indicate that in the of health the revision of the Act on Physical Culture from 2002, which reduced the number of school's physical education classes, is a debatable issue. (Contains 2 tables and 1 figure.)