A study of the inclusive polarization of hyperons produced by 400-GeV/c protons incident on nuclear targets has been performed at Fermilab. The polarization P of the has been mapped over a large range of xF and pT to good precision for pT up to 3.8 GeV/c. The magnitude of the polarization at fixed xF rises with pT to a plateau at about 1 GeV/c, and the size of the plateau increases monotonically with xF. The » were found to be unpolarized for pT<2.4 GeV/c. A target-nucleus dependence for the polarization has been observed.