Background: The previous knowledge which a student brings with him to university is an important item which eases adaptation and permanence at the university. When a diagnostic exam to evaluate the knowledge students have in Mathematics, their deficiencies from previous studies become clear. At the Instituto Tecnológico de Sonora a diagnostic exam was prepared and given to students who were seeking to enroll in the field of Engineering for the 2016 and 2017 school years. Material and methods: In the study 1,922 students seeking enrollment in 2016 and 1,184 seeking enrollment in 2017 participated. The exam for the 2016 group was given on computers face-toface in the classroom while the 2017 group was given a distance exam on-line. Results: The students who took the exam in 2017 received higher percentages of correct answers on the exam than the students from the 2016 group. Conclusions: However, both groups showed deficiency in mathematical knowledge in various areas such as Arithmetic (problems with applications in context), Geometry, Algebra (factoring, liner equations and 3x3 lineal equation systems), Analytical Geometry (the four cone figures) and in Calculus (derivative of transcendental functions, limits of a function and maximums and minimums).