Abstract
The present study reports (to the knowledge of the investigator) the first careful factor analysis of the Social Interest Index (SII), a measure of Adler's concept of social interest. The test item responses of 416 students from heterogeneous college classes were intercorrelated and factor analyzed. Four factors emerged which accounted for 37% of the total variance. Results are discussed in terms of the congruence between the obtained and hypothesized factors. Recommendations are made for future factorial validity research with the SII, as well as for ways to improve the structure of the scale.