Opioid receptors belong to the superfamily of G protein coupled receptors and are primarily responsive to opiates to produce analgesia, but opiates also produce a variety of side effects. One goal of computational chemistry is to determine the interactions between a ligand and protein. This knowledge could allow for the development of opioid agonists without current side effects. Homology models of human mu, kappa, and delta receptors were developed based on a previously validated homology model of the endothelial differentiation gene. Docking of native ligand, morphine, was performed. The results indicate that the docking studies identified the actual active site in the model. Morphine had hydrogen bonds to Asp211, His361, and Ser381 in the mu receptor, and hydrogen bonds to Asp138 and His291 in the kappa receptor. Morphine had hydrogen bonds to Asp128 and His278 in the delta receptor. This correlates well with experimental data. We predict, based on the models, that mutation of Ser319 to alanine in the mu receptor would confer delta type binding. We further predict that mutation of Tyr312 to tryptophan in the kappa receptor would confer mu type binding. If Tyr312 were mutated to leucine, the resulting receptor would have delta type binding.