The main objective of this monograph is to provide the undergraduate and post graduate students of statistics with an adequate understanding of the basic concepts of the theory of statistical estimation. It is based mainly on the class-room lectures on estimation theory which the author taught for more than four decades. A number of various types of problems have been worked out which are expected to help the students understand and apply the general theoretical results in various typical cases. It has been prepared keeping in view the syllabi of many of the Indian Universities. This monograph would also help those who are preparing for the entrance test of IIT JAM.