Revision with unchanged content. This book explores design tools based on evolutionary computation (EC), oriented primarily toward conceptual design of architectural and civil en ginee ring structures. EC tools are well suited for exploration in a way which pro motes creative design. The multiplicity of solutions generated by EC tech niques is less likely to cause design fixation, and so promote a more thorough ex plo ration of possible solutions. The use of such tools also allows the de si g ner greater latitude in exploring design criteria, such as aesthetics, by utilizing an interactive human-computer interface. This book begins with a survey of tech niques that have been used in early phases of architectural design, and estab lishes a set of successful attributes, which are then discussed in the con text of EC techniques. Finally, a specific implementation developed by the au thor is described. Several examples are given in the area of architectural en gi nee ring, and comparisons are made with results obtained with more con ven tio nal optimization tools. This book is especially useful for designers in ter es ted in new methods for generating and exploring structural form, and is acces sible to non-programmers in either field.