John L. Holland’s theory of vocational personalities and work environments has had massive influence on the practice of career counseling, the classification of occupations, and the conduct of career development. Our principal intent in this book is to make public Holland’s autobiography entitled, “My Life with a Theory.” We have also included book chapters and journal articles that we believe will enhance reader understanding of both the theory and the scientist. The material assembled in this volume is also intended to serve as a resource for teaching graduate students about Holland’s theory, the scientist, and the tools and methods he developed. The book provides in one place original statements of the theory by Holland, articles about the nature of the scientific and professional contributions widely used by counseling professionals today, and evaluations (admittedly with a positive bias) of those contributions. Indeed, we expect that the main audiences for this book will be counselor educators, counseling psychology faculty, career practitioners and graduate students in counseling and psychology.