Pair programming is a practice in which two programmers work collaboratively at one computer on the same design, algorithm, code, or test. Pair programming is becoming increasingly popular in industry and in university curricula. A family of experiments was run with over 1200 students at two US universities, North Carolina State University and the University of California Santa Cruz, to assess the efficacy of pair programming as an alternative learning technique in introductory programming courses. Students who used the pair programming technique were at least as likely to complete the introductory course with a grade of C or better when compared with students who used the solo programming technique. Paired students earned exam and project scores equal to or better than solo students. Paired students had a positive attitude toward collaboration and were significantly more likely to be registered as computer science-related majors one year later. Our findings also suggest that students in paired classes continue to be successful in subsequent programming classes that require solo programming.