Lowering the dropout rate of incoming mathematics and science students, and enhancing the provision of mathematics support for freshmen are two important aims of the University of Amsterdam. The approach recently adopted to support first year students is to set up a diagnostic pretest and posttest and use these tests to identify students being at risk of failing their mathematics courses and other modules in the first year. Follow-up procedures are implemented and computer algebra based assessment and practise of mathematics skills play an important role in it. In this paper we describe this approach and its success. (Contains 1 table and 3 figures.)