This book presents some of the main areas and results of general metamathematics. In addition to standard results of GAdel et al. on incompleteness, (non-)finite axiomatizability, interpretability, etc., it contains a thorough treatment of partial conservativity and degrees of interpretability. The method of arithmetization plays an all important role in the book. The reader is assumed to be acquainted with this method and with the elements of recursion theory. The book will be useful as a textbook for a graduate student course - there are many exercises - and as a reference text for researchers.