This collection of quantum mechanics problems has grown out of many years of teaching the subject to undergraduate and graduate students. It is addressed to both student and teacher and is intended to be used as an auxiliary tool in class or in self-study. The emphasis is on stressing the principles, physical concepts and methods rather than supplying information for immediate use. The problems have been designed primarily for their educational value but they are also used to point out certain properties and concepts worthy of interest; an additional aim is to condition the student to the atmosphere of change that will be encountered in the course of a career. They are usually long and consist of a number of related questions around a central theme. Solutions are presented in sufficient detail to enable the reader to follow every step. The degree of difficulty presented by the problems varies. This approach requires an investment of time, effort and concentration by the student and aims at making him or her fit to deal with analogous problems in different situations. Although problems and exercises are without exception useful, a collection of solved problems can be truly advantageous to the prospective student only if it is treated as a learning tool towards mastering ways of thinking and techniques to be used in addressing new problems rather than a solutions manual. The problems cover most of the subjects that are traditionally covered in undergraduate and graduate courses.