In this paper we summarize our recent studies of the effects of local alloy disorder on the properties of DX levels. A single emission rate is observed in GaAs where all Si-donors have identical local environments. In contrast, three discrete emission rates are observed in dilute AlGaAs alloys, suggesting that the group IV donor moves towards the interstitial site, thereby "selecting" three of the twelve surrounding group III atoms. We present evidence for an ordering of the DX levels consistent with Morgan's model of a deepening potential well for the DX level as Al atoms are subsequently substituted for Ga atoms near the relaxed donor. These conclusions are consistent with earlier calculations of Chadi and Chang. © 1991 AIME.