This book is different from the first edition. There are three entirely new chapters: 2,6 and 9. I have also included new sections in chapters 1,4 and 8. Moreover, the remaining chapters, 3, 5 and 7, have been revised and updated. In chapters 2 and 6 I felt it was necessary to include the main alternative theories ofconsumer and company behaviour along with the neo-classical models. The book contains four chapters oftheory - 1, 2, 5 and 6 - and four chapters with theoretical and empirical applications - 3, 4, 7 and 8. Finally, chapter nine looks at choices made under conditions ofuncertainty. September 2002 P. Coto-Millan Preface to the First Edition Grateful acknowledgment is made to CICYT (Comision Interministerial de Ciencia y Tecnologia), National Plan R+D, Projects N-TXT96-2467 and N TXT98-1453 for its fmancial support. This text presents the economic theories on Utility and Production. In addition, such theories are used to explain the real problems of consumers and fIrms and several studies carried out by the author are displayed.