The author presents a short survey of the main hypotheses concerning the time and causes for the foundation of Chersonesus Taurica, as well as an analysis of a series of relevant archaeological sources. More than two hundred objects may serve as archaeological sources for determining the time of the foundation of the city. They come from the early layers of the site and from burial complexes of the necropolis. Relevant epigraphic evidence includes 45 ostra-ka. The data drawn from them shows that the Greek apoikia began to exist in this place about the second quarter of the 5th century BC. This conclusion does not contradict the data of the written sources about the foundation of Chersonesus. In the first half of the 5th century BC Heraclea Pontica was politically and economically interested in establishing a new apoikia in the south-western Crimea and had an opportunity to found it. Athens' policy regarding Delos in the late 6th and the first half of the 5th century BC forced the Delians to join the project. The foundation of the apoikia was a part of Heraclea's territorial expansion. During the first 50-70 years of its existence Chersonesus could have served as a trans-shipment point and staging post, a port of its metropolis on the northern coast of the Pontos Euxeinos. Anthrop-onymic data shows that the population of the colony was mixed. However, scarcity of archaeological sources and succinctness of the written evidence do not allow to ascertain the social and political structure of the colony during the first decades of its existence. Besides, it is not impossible that new groups of population were constantly coming to the colony during the 5th or even the early 4th century BC, changing the number of its inhabitants and the social structure of the community.