Individuals differ in the degree to which they see themselves as behaving and feeling similarly or differently in different situations and at different times. This dimension of the self-concept, which is conceived to extend from strong constancy of the self-concept at one extreme to marked variability at the opposite pole, is designated as self-pluralism. An inventory for the assessment of degree of self-pluralism—the Self-Pluralism Scale (SPS)—is presented, and the correlations of this scale with other relevant personality measures are reported. Several studies utilizing the SPS are presented. The results indicate that self-pluralism is negatively related to psychological adjustment, positively related to long-term real-life variability, and negatively related to age.