The article is devoted to the analysis of the structural changes in the civic community of Sparta at the end of the 5th–beginning of the 4th century ВС. The analysis of the sources shows that the civic community began to disintegrate and the new social group of Hypomeiones appeared just in this period. The author considers in detail questions connected with the reasons, time of appearance and status of this category of the Spartan citizenry. Particular attention is paid to the mechanism by which full citizens have lost some of their rights and have fallen down the social ladder, becoming Hypomeiones. The author examines all the sources related to this issue and shows as much as possible the extent to which this topic has been dealt with in Russian and Western historiography.