This book is about interpreting seismic data on computer screens. It is intended for both skilled interpreters who are new to interpreting on computers, and to some extent for people who are novices at interpretation itself. It should be particularly useful to geophysicists who left the industry and are now returning, only to find that a whole new way of interpreting has come along while their backs were turned. It should also be useful for (1) geologists and petroleum engineers to get an idea of the capabilities of the geophysicists they work with, and of the interactive systems those geophysicists have available, systems that they may be able to use in their own specialties, (2) managers, processors, technicians, and secretaries to get some familiarity with what the geophysicits are doing at those fancy machines with the bright-colored displays, (3) students to add practical information to the theory taught in most courses. For anyone who is new to interactive seismic interpretation it is the book to read as a preliminary to a manual written for a specific interactive interpretation system. This book does not explain basic seismic interpretation. That is given in two other books. This present book concentrates on the ways interpreting is done with a computer.