The PSP is a defined family of processes that engineers can use to write module-sized programs. It is introduced with a one-semester graduate-level course where engineers develop ten programs and write five analysis reports. They practice various methods, obtain measurements, and analyze these measurements to help them understand and improve the way they work. This course has been taught in several universities and is being introduced in a number of industrial software organizations. While individual performance varies widely, data on 104 students and engineers show reductions of 58.0% in the average number of defects found per 1000 lines of code (KLOC) and reductions of 71.9% in the average number of defects per KLOC found in test. Estimating and planning accuracy are also improved while the average percentage improvement in lines of code developed per hour was 20.8%.