With the expansion of the discipline of public administration, the need for literature on administratvie theory is being increasingly felt. This book in an attempt to fill this gap; albeit in part. The book provides an account of the ideas and contributors of twenty-one thinkers to the discipline. Each chapter covers an outline of the thinger's life, writings, principal contribution to the theory and a critical evaluation. This volume is weaved the study and teaching of public administration, political science, sociology and management. It offers a single source of reference on the theory of public administration; particularly the contribution of select thinkers. In this second and revised edition one chapter on administrative theory and two thinkers have been added. All chapters have been revised. Over the years the book gained recognition and has become a compulsory reading to the students and scholars of public administration. It is also an important source book for those appearing for the competitive civil service examinations at national and state levels in public administration and management.