Researchers examine a Constructive Developmental (CD) view of leadership development. While past research has found that upper level executives tend to possess higher leadership levels, there exists a lack of empirical research examining the relationship of CD leadership theory with actual performance ratings. This study examines the relationship of CD theory as applied to the study of leadership and utilizes a robust measure of leadership effectiveness, a 360-degree feedback instrument. The study investigates as to whether leadership developmental level (LDL) predicts leadership effectiveness, and specifically which types of rating sources differentiate leaders at different LDLs, as well as which rater sources more effectively predict LDL. Finally, the analysis includes a discussion of the implications for selection and leadership development.