In the present study 25 males and 11 females were monitored for an 18- to 20-month training period during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third period were concluded with a 15-, 25-, and 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Before and after three contests of 15, 25, and 42.195 km, the plasma concentration of testosterone, cortisol, and dehydroepiandrosterone sulfate (DHEAS) were determined. The decrease of plasma testosterone concentration in males was dependent on the distance of the contests. Moreover, the plasma testosterone concentration was increased in males during the course of the training period. In females no clear relation between plasma testosterone levels and the contests could be observed, and no changes in basal levels were found in the course of the training period. DHEAS seems to be a more useful stress marker than the plasma cortisol concentration. The plasma levels of this hormone remained elevated both in males and females for 1-2 days after the contests. The amplitude of DHEAS increments, however, was greater after the marathon.