This book provides the reader with a self-study, step-by-step guide to doing thermodynamic calculations in Aspen Plus (Version 8.x). This is done by providing actual screen shots of the Aspen Plus interface to solve example problems of various types, including vapor-liquid, liquid-liquid, vapor-liquid-liquid and chemical reaction equilibria, and simple applications to liquefaction, distillation and liquid-liquid extraction. Because it has been designed for self-study use, it is meant to be assigned to students to use out of class, and not as an in-class textbook. It does not attempt to teach the basics of thermodynamics; it stresses the application of thermodynamics to realistic problems.