The development of results of five national level sprinters (Group A) was followed up during a training period of two weeks at an altitude of 1860 m aiming at increase of strength and speed and after it. Changes in anaerobic capacity were monitored by making blood lactic acid determinations, and occurrence of any overstrain by serum testosterone, cortisol, growth hormone and SHBG (sex hormone binding globulin) determinations. A control group (Group B) trained simultaneously according to a similar programme at sea level. Maximal 150 m running speeds increased in Group A significantly during the two weeks at the altitude of 1860 m (p less than 0.001). No such increase was observable in Group B. Maximal 300 m running speeds and maximal lactic acid concentrations after running did not increase significantly in either group. Serum hormone levels did not change significantly either, in either group. Training at an altitude of 1860 m to increase strength and speed significantly improved results at the shorter distance of 150 m but had not significant effects on anaerobic capacity or on serum testosterone, cortisol, growth hormone or SHBG levels.