The controlled doping of n- and p-type AlxGa1-xAs has been studied for the dopant elements, C, Zn, Si, and Sn. Both the incorporation characteristics and the electrical properties of these dopants are reviewed and discussed fo AlxGa1-xAs grown by th metal-organic vapor phase epitaxy (MOVPE) technique. The incorporation of Si from SiH4 and Si2H6 is dominated by heterogeneous and homogenous reactions respectively and represents the best understood of the doping systems. Zinc and carbon both possess complex dependencies on the MOVPE growth system parameters. The electrical behavior of n-AlxGa1-xAs is dominated by the presence of the DX center. The relationship between this center and the electrical behavior of the material must be understood in order to properly characterize the doping behavior in AlxGa1-xAs layers and structures. © 1989.