Eighty-four male rats were tested to determine their preference for one of two distinctive places in an experimental space. After an initial determination of place preference, rats were assigned to six groups. They were then subjected to procedures to condition a place preference using doses of beta-casomorphin, a standard dose of morphine, or placebo. Subsequently, rats were tested for place preferences. No evidence emerged indicating that injections of beta-casomorphin conditioned a place preference, but evidence indicated that morphine conditioned a place preference. Consequently, systemically administered beta-casomorphin has very limited or no reinforcing properties similar to those of morphine. Ingestion of milk products containing beta-casomorphin is not likely to become the focus of an addiction.