Some of the slaves on offer at markets in Classical times were children of slaves, born into slavery. Others were the victims of war, piracy and the exposure of unwanted infants. In the case of Athens, it had been forbidden by Solon, at the start of the sixth century to throw an Athenian citizen into slavery on the grounds that the latter was in debt. Therefore, slaves generally came from elsewhere. There were monthly markets where slaves were bought and sold held in the mining district around Sounion, and inside the city wall in the Agora.

The market price varied according to age, sex, origin, physical strength and mental agility. Slaves exchanged for money were called argyronetoi ('silver-bought'). A late fifth-century slave-sale inscription discovered in Attica informs us that children fetched 70 drachmae (but uneducated children, 50) and adult males fetched 200 drachmae. These figures showed a sharp divergence in the case of well-known individuals: When the philosopher Plato was sold as a slave at Aigina, his purchaser paid two or three thousand drachmae. There were also slaves who were exchanged for salt, and these were called alonetoi ('salt-bought').

Slaves fell into various categories depending on what work they did: house-slaves, mine workers, slaves 'living out' [khoris oikountes], and public slaves. The slave was seen as an acquisition - a "soulless chattel" (ktema apsykho) - to be bought and sold like any other movable asset: rented out, bequeathed, or made a present of. Having no legal status, initiative or opinions, the slave was attached to his master and was in effect (as Aristotle makes clear in the Politics) somehow part of his master, an animate, though separate part of his body.

Any free person, whether citizen, metic or foreigner, could become a despotes, a slave-owner. There was a small number of slaves who were charged with the city's security and they were the property of the deme of Athens. As an item of ownership, recorded on lists of assets but not on the city rolls, the slave did not have the right to own property, unless the master allowed him to keep back part of what he earned for services rendered. Legally, however, this income belonged to his master.

The right of life was guaranteed to slaves in Athens. But although a master was not allowed to kill his slave, Athenian law did not forbid a slave-owner to torture or maltreat slaves. Where working conditions were inhuman, as in the silver-mines at Lavrion, we can be sure that the slave mortality rate was high.