PbTe single crystals are equilibrated with (Pb,Zn) alloys of various compositions at 700 and 800 °C and quenched to room temperature. Hall-effect and solubility measurements of these crystals indicate that zinc acts as a donor in PbTe, being incorporated in interstitial sites as Zni compensated by electrons. A complete defect model for Zn-doped PbTe is arrived at, which predicts the behavior of PbTe crystals in metal-rich as well as Te-rich atmospheres.