General socioeconomic conditions as well as the physical environment have undergone remarkable changes in Hungary during the past 30 years. Unfortunately, these positive processes have resulted in a reduction of habitual physical activity along with unfavorable changes in dietary habits. Therefore, the purpose of the present study was to compare some selected morphological and functional parameters of 7-14-year-old Hungarian schoolboys living in the middle of the 1970s and at the beginning of the new millennium. It was hypothesized that there would be significant differences in morphological and functional characteristics of the Hungarian schoolboy populations, because they were assessed 30 years apart. Means of height, body mass, body mass index (BMI), the sum of five skinfold tests, percentage of body fat, and two running performance times (400 m and 1,200 m) of the boys (N = 3,672) studied in 1975 were compared to those of the boys (N = 3,758) in 2005. Data were analyzed using two-tailed independent samples t tests (p less than 0.05). We observed significant secular changes in body mass and height. In addition, boys in 2005 had significantly more subcutaneous fat compared to 1975. The running times for the two distances were significantly poorer at the time of the second investigation. The remarkable and unfavorable changes in body composition and cardiorespiratory performance were attributed to the continuously decreasing intensity of habitual physical exercise and a lifestyle that had become more sedentary (watching TV, playing computer games, etc.). Radical interventions are necessary to reduce these risks associated with the high prevalence of cardiovascular disease in Hungary, and the challenge to resolve the problem requires combined efforts at the educational, societal, corporate, and governmental levels. (Contains 2 tables and 4 figures.)