Through immigration and the import of slaves the population of Ostia rose to fifty thousand, including seventeen thousand slaves.

Most slaves were taken to Ostia from Egypt, the Middle East, and Turkey. The breeding of slaves must also have been a profitable trade.

Most families had at least one slave, and there were many Imperial slaves, working in the harbour and store-buildings.

Many slaves were manual labourers, but others were important people, such as clerks and accountants.

The most frequent slave-name is Felix: "Happy".