Book excerpt: This book presents a detailed description of the Think Aloud Method, which was developed to facilitate knowledge acquisition and problem-solving by asking the participant to think aloud while solving a problem. The Think Aloud Method is based on the premise that people are often able to verbalize their thoughts as they solve a problem, and their resulting behavior can be analyzed to answer questions about problem solving behavior. This method is useful for psychological research on problem solving behavior, as well as for knowledge acquisition in the context of building expert computer programs. In many cases the Think Aloud Method is an invaluable source of information for psychologists and knowledge engineers. The Think Aloud Method is intended for two types of readers: social scientists who want to use the Think Aloud Method for research on cognitive processes, and knowledge engineers who wish to use the method for knowledge acquisition. The book is made accessible to both audiences with short introductions to several issues that are basic knowledge for one readership, but that are not part of the standard knowledge of their community. Introductory sections on those topics relevant to both communities are also included. The Think Aloud Method will prove a welcome addition to work in this exciting area.