This paper summarizes the Thomas and Cross models on psychological nigrescence and reviews the empirical studies which have been conducted to validate these models. "Nigrescence" means the "process of becoming black", and as these models attempt to depict the various stages black Americans traveled in seeking a new identity during the late l960's and early 1970's, the models in effect speak to the psychology of the process of becoming black. A comparison of the two models indicates that they are not as similar as one might expect. The Thomas model begins at the point where the black person has already begun to change; consequently, it does not incorporate stages that are similar to the first two stages of the Cross model. While the Cross model has only one transition stage, Thomas's scheme has four. Only the fifth stage of each model, that of internalization, is similar. Both models, however, place considerable importance on understanding the dynamics of the Negro personality and/or worldview, and each ends with an analysis of internalization. A final section of the paper reviews eight empirical studies which have been generated by these models. It is noted that these studies have advanced the knowledge about the nature of the transition steps between the "old" and "new" black identity. However, in placing more emphasis on the analysis of the process of becoming black, the studies have not adequately discerned the structure, dynamics and functions of the new identity as it operates under "steady state" rather than change or crisis conditions. The empirical studies have produced three new research tools that will contribute to the sophistication of research on the psychology of nigrescence. (Author/AM)