The purpose of this article is to review the familiarization protocols and other factors used in laboratory and field testing studies implemented to measure the cardiorespiratory fitness of persons with mental retardation. Test selection issues, pretest familiarization procedures, and motivational strategies will be discussed. Little information is available to identify specific guidelines for familiarizing a subject with a specific protocol prior to cardiorespiratory fitness testing. The recommendations suggested in this article provide valuable and necessary information for researchers interested in the measurement of cardiorespiratory fitness of persons with mental retardation.