This paper describes a gateway testing program designed to ensure that students acquire basic skills in freshman calculus. Students must demonstrate they have mastered standards for "Absolutely Basic Competency"--the Calculus ABCs--in order to pass the course with a grade of C or better. We describe the background, standards, and testing program. Based on three years of objective data, together with subjective impressions, we conclude that the program is effective in encouraging many students to master the basics. We also describe improvements currently in place, including web-based test generation. (Contains 2 tables, 2 figures, and 1 footnote.)