Human research using drug discrimination procedures is reviewed. Originally developed in the animal laboratory, drug discrimination procedures have been suggested to provide an index of subjective drug effects. Human research provides unique opportunities to assess the relationship of subjective and discriminative drug effects, since only in humans can the two be assessed concurrently. Methods used for assessing subjective effects and methods used for training and assessing drug discriminations in humans are described. Research data are then reviewed and discussed with respect to what they suggest concerning the relationship of subjective and discriminative drug effects to one another. It is concluded that there is a relationship, though not a simple one, and that the nature of the relationship is likely to be influenced by the procedural details of specific drug discrimination training and testing paradigms. Recommendations for future research are made.