This book introduces two most important aspects of modern analysis: the theory of measure and integration and the theory of Banach and Hilbert spaces. It is designed to serve as a text for first-year graduate students who are already familiar with some analysis as given in a book similar to Apostol's Mathematical Analysis. t This book treats in sufficient detail most relevant topics in the area of real and functional analysis that can be included in a book of this nature and size and at the level indicated above. It can serve as a text for a solid one-year course entitled "Measure and Integration Theory" or a com prehensive one-year course entitled "Banach Spaces, Hilbert Spaces, and Spectral Theory. " For the latter alternative, the student is, of course, required to have some knowledge of measure and integration theory. The breadth of the book gives the instructor enough flexibility to choose what is best suited for his/her class. Specifically the following alternatives are available: (a) A one-year course on "Measure and Integration" utilizing Chapters 1 (Sections l. l-1. 3 and 1. 6), 2, 3, 4, portions of 5 (information on Lp spaces), and portions of 7 (left to the discretion of the teacher). (b) A one-year course in "Functional Analysis" utilizing Chapters 1 (Sections 1. 4-1. 6), 5, 6, 7 (Sections 7. 4 and 7. 6), and the Ap pendix. t T. M. Apostol, Mathematical Analysis, 2nd ed., Addison-Wesley (1974)."