This book gives a treatment of exterior differential systems including both the general theory and various applications. Topics include: a review of exterior algebra, simple exterior differential systems, the generation of integral manifolds through the solution of a succession of initial- value problems, involution, linear differential systems, tableau and torsion, the characteristic variety of a differential system, prolongation, the Algebra of a linear Pfaffian system, and an introduction to Spencer Theory. Much emphasis is placed on the general theory while many examples are given.