This qualitative study sought to identify current principal professional development practices in four school systems in Georgia and to examine them by applying the principles of adult learning theory. The cross-case analysis of principal professional development initiatives in four school districts revealed nine common practices: connecting professional development to career development; individualizing professional development; engaging multiple sources of professional development; adapting, not adopting, externally provided professional development; aligning and focusing professional development; ensuring ongoing scheduled professional development; encouraging mentoring relations; providing data-informed and job-embedded professional development; and strategic planning of principal professional development. Although these practices possessed certain characteristics of adult learning--they were problem centered, relevancy oriented, and goal oriented--they were, however, rarely self-directed. By examining current principal professional development practices through the lens of adult learning theory, these findings contribute new knowledge about current principal professional development and offer implications for the use of adult learning theory in planning and providing principal professional learning.