Program evaluation is relatively new as a recognized area of organized activity. It was only in the 1970s that the first journals with *evaluation* in the title were launched, the first professional organizations were formed, and the first textbooks were published. One of the earliest of those textbooks was the first edition of this one, *Evaluation: A Systematic Approach*, authored by Peter Rossi, Howard Freeman, and Sonia Rosenbaum and published in 1979. With the benefit of hindsight, it is easy to recognize what a landmark that was. The publication of that comprehensive text at that time marked the point at which program evaluation had come of age as a field of endeavor with its own distinct identity, concepts, methods, and practices.