In order to evaluate physiological characteristics in young male ballet dancers, 27 boys (aged 9 to 16 years) who participated in a boys' dance course during the Kuopio Dance and Music Festival in June 1988 were studied. In general, the boys had started dancing at the age of 8.6 years and had been training for 4.1 years. They had, on average, three dancing sessions per week and the mean time spent on dancing was four hours per week. In the study, some anthropometric measurements were taken, the maximal oxygen uptake (VO2 max) was measured by a cycle ergometer test and the explosive strength and the mechanical power of lower extremities were evaluated by a jumping test. The results indicate that boys who train in ballet are in general moderately lean, have relatively small body size and a high degree of flexibility. The younger boys especially have only moderate aerobic power, but both explosive strength and mechanical power in leg muscles are good in ballet trained boys.