No, no downside to owning Slaves in Civ 3, except they don't work as fast as your workers!
In addition to what Aabraxan said, if you add slaves from an extinct AI to a city, there is no increase in the chance of the city flipping. (Viz. A city can't flip to an extinct civilization!)
In addition to what Aabraxan said, if you add slaves from an extinct AI to a city, there is no increase in the chance of the city flipping. (Viz. A city can't flip to an extinct civilization!)


