The problem of point‐defect equilibria in compound semiconductors is considered. It is shown that the expected donor or acceptor properties of a defect in a compouud are entirely independent of the type of binding (ionic or covalent) in the compound. From general thermodynamic arguments it is shown that the number of degrees of freedom of a compound in internal equilibrium is one more than the number of chemical constituents of the compound independent of the number and nature of the defects it contains. The consequences of this are discussed and it is shown how mass action laws result, describing internal reactions among the defects. An example from the literature is presented to illustrate the methods of setting up and solving these mass action laws and how the solutions might be compared with experimental results. Finally, association between oppositely charged defects in solids is discussed.