Microstructural control in heterogeneous high-Cr white cast irons is believed to be important by many tribologists for the accurate prediction of wear properties. To this end, the U.S. Bureau of Mines is working toward developing a systematic and quantitative approach for the microstructural control of these commercially important irons. Current research on high-Cr white cast irons at the U.S. Bureau of Mines, Commonwealth Scientific Industrial Research Organization (CSIRO), Australia, and elsewhere is reviewed. In the first part, special consideration is given to theories and practices that influence the structure and morphology of the brittle carbide phases and govern the ferrous matrix structure, proportion of phases and eventual hardness. The second part will discuss the role of these microstructural constituents in determining the abrasion and impact properties of high-Cr white cast irons with emphasis on the role of retained austenite.