This book deals systematically with the mathematical theory of plane elasto-statics by using complex variable methods, together with many results originated by the author. The problems considered are reduced to integral equations, Fredholem or singular, which are rigorously proved to be uniquely solvable. Particular attention is paid to the subjects of crack problems in the quite general case, especially those of composite media, which are solved by a unified method. The methods used in this book are constructive so that they may be used in practice.