Empirical validation of the Self-Identity Development Model of Oppressed People (SIDMOP) prompted the choice of a multi-methodological approach that would test the underlying theory and not the participants' ability to perform a matching task. Few identity developmental models of oppressed people have been systematically developed, and even fewer have been empirically validated. SIDMOP is based on a nontraditional psychological framework that theorizes a nonlinear growth process, while most measurement tools in the field are based on linear thinking. Validation of current research on oppressed people has led to the development of attitudinal and cognitive measures such as the Racial Identity Attitude Scale (RIAS), and the Gay/Lesbian Identity Questionnaire. SIDMOP has been developed to understand others in an experiential way. The model was developed systematically and thoroughly, using an emic process, and additional clinical research may be all that is necessary for validation. However, if the model is to be developed for further research, content specific instruments need to be developed for each oppressed group that include the following issues: (1) the effect of the participant's world view, selective memory, and social desirability; (2) the possibility of "false positives"; and (3) the effect of the participant's age and current developmental tasks. (FMW)