We present a review of both theoretical and experimental studies of stress effects on the solubility of dopants in silicon and silicon-germanium materials. Critical errors and limitations in early theory are discussed, and a recent treatment incorporating charge carrier induced lattice strain and correct statistics is presented. Considering all contributing effects, the strain compensation energy is the primary contribution to solubility enhancement in both silicon and silicon-germanium for dopants of technological interest. An exception is the case of low-solubility dopants, where a Fermi level contribution is also found. Explicit calculations for a range of dopant impurities in Si are presented that agree closely with experimental findings for As, Sb and B in strained Si. The theoretical treatment is also applied to account for stress effects in strained SiGe structures, which also show close correlation with recently derived experimental results for B-doped strained SiGe which are presented here for the first time.