PROBLEMThe ego is a hypothetical construct used with some lack of clarity but with high frequency in explanations of personality development and functioning. The ego is customarily defined in terms of its functions, as adaptation to reality and interpersonal relations, and the effectiveness of ego functioning is called ego strength. The problems of assessing ego strength have been described by Herren(*) in a review of ego strength measures. A major difficulty is that since ego functioning involves various types of behavior, ego strength measures have been varied in their approach. At the same time, little is known about the interrelations of ego strength measures, and questions remain as to what inferences can be drawn from a particular test of ego strength. The present study attempts to clarify the composition of ego strength by investigating the relationships among 9 measures of ego strength. The particular measures were selected in terms of covering a range of ways to estimate ego strength. METHOD Sample.The Ss were 40 college students, 20 males and 20 females, mean I& 118, and an average age of 18 at the inception of the study. They were selected at random from the freshman class and tested over a two year period with 9 ego strength measures. Eight of the measures were obtained in the first year with a sample of 40 but one measure, derived from the Rorschach, was gotten in the second year with a sample restricted to 33 of the original Ss.Tests and Procedure. The ego strength measures were:1. The ego strength factor (ESF) of the 16 PF, designed to measure the capacity for integrated expression of emotional energy. ( I ) 2. The Z score of the Bender-Gestalt(lI), primarily involving visual motor functioning, and administered as a grou test. High scores on this test are in the direction of less ego strength, so that the predicted correitions would be negative between Z and other ego strength measures.The perceptual range (PR) and perceptual organization (PO) scores of the TAT('), extended by the authors to cover all of the 10 TAT cards used in this study. These scores are concerned with ability to organize perceptions and to develop details of perce tions with prescribed limits. The inclusion of this method was based on the suggestion of the T A g as a potential murce for estimating ego strength@), though the method had not been previously used as a formal estimate of ego strength. The TAT was administered as a group test. and stability, moral attitudes, sense of reality, personal adequacy, and anxiety. While the v a d i t y of this measure is in question, it was included because of the frequency of its usage as an estimate of ego strength.6. The ego strength-ego weaknes factor (ESEW) comprising 10 MMPI scales(g), with an ap arent emphasis on ego weakness, so that the expected correlations would be negative with regarlto the ego strength measures other than Z. 7. I& from the Otis S A Test of Mental Ability, included because intelligence is generally considered an important ego function.8. The Rorschach Prognostic...