Since 1989, the Mathematics Education Project (PmatE--Projecto Matematica Ensino) has developed several strategies to improve the success of students in Mathematics. The most important of these are mathematical games for all grades above primary school. The online evaluation of Mathematics subjects is one of PmatE's goals. The implementation of an on-line diagnosis test--TDmat (Teste Diagnostico de Matematica), mandatory for all students enrolling for the first time in Science and Engineering courses at the University of Aveiro, was the approach chosen to evaluate the mathematical competences of these students. TDmat is a computer test with automatic evaluation in which the analysis of results is done automatically. This paper describes how it is conceived as well as the main results and conclusions drawn from evaluations of the school years 2003/2004 and 2004/2005. (Contains 18 figures, 1 table and 1 footnote.)