The Euboeans, including the Eretrians, seem to have been pioneers in the movement of Greek colonization that took place in the 8th century BC. Literary and archaeological evidence both agree on this issue. Although it is often difficult to distinguish Eretria's role from that of other Euboean cities, we know that, along with its neighbor Chalkis, it took part in the foundation of Pithekussai, one of the oldest Greek overseas settlements, situated on the island of Ischia in the Gulf of Naples, and then in the foundation of Kumai. In Chalkidike (northern Greece), several colonies were certainly of Eretrian origin: Methone, Dikaia, and Mende.
The search for metals (of which southern Italy and northern Greece were potential sources of supply) was probably one of the main incentives of colonization. But economic interests were not limited to metal alone. Once commercial networks were established, all sorts of products could be exchanged. Other reasons, peculiar to the city itself, also encouraged settlers to leave. We know that such enterprises were sometimes motivated by political, social, or economic crises (stasis). The community of Eretria, which was undergoing a profound evolution during the 8th century BC, may have experienced internal conflicts that led some of its members to embark upon a colonial adventure. In return, the experience of these new founders may have accelerated the political development of the young city.
Thus Eretria took a major part in this first stage of Greek colonization. But while Eretria seems to have played a leading role in this trend during the 8th century, it was later challenged and surpassed by other cities such as Corinth, and Miletos in Asia Minor, Eretria's powerful ally during the entire Archaic Period.