The article is devoted to the analysis of the ancient tradition about the contest of two Spartan kings, Kleomenes and Damaratos. The greatest part of references to Kleomenes and Dam-aratos is found in Herodotus' History, which may be considered as the main source for our theme. The fight for superiority between Kleomenes and Damaratos caused their own personal catastrophe and brought about the weakening of the king's power itself. The law passed in 506 BC limited the kings' commander-in-chief power. Ephors got the ability to interfere in the military sphere, which had been closed to them before. It may be concluded that the ephorate actually became the highest state executive in Kleomenes' epoch. For the first time it could use its potential resource in the fight against kings' power.