Gateway tests provide a means of assuring that students in reformed precalculus and calculus courses acquire the algebraic and computational skills needed in courses following these, while allowing the focus of the course to be on the conceptual understanding intrinsic to the reformed courses. However, logistical difficulties plague the pencil-and-paper administration of these tests, significantly decreasing their usefulness. To address these difficulties we have implemented an on-line version of the gateway tests which allows students to practice the skills on their own and take the test for a grade in a proctored environment. We report on the details of our implementation and assessment of our system, including our administration procedures and lab use. Our assessment included evaluation of students' perceptions of the effectiveness of the program and their actual skill acquisition, and showed that the students' skills improved in the course of the on-line gateway testing. (Contains 4 tables and 3 footnotes.)