BACKGROUND Formative evaluation is a range of formal assessment employed by professors during the teaching process in order to modify curriculum activities, to improve student attainment. For students, it is helpful to evaluate their learning process. Although recommended, it is seldom used. AIM To evaluate the perception and performance of medical students subjected to formative assessments during an integrative clinical course. MATERIAL AND METHODS Fourth year medical students that participated in a multiple choice formative assessment, similar to the final exam during 2007 and 2008, responded a survey about the usefulness and quality of such assessment. Student achievement was expressed as the percentage of correct answers of the tests. RESULTS The formative assessment was answered by 99% of students. In 2007 97% of students considered the experience as excellent or very good and 92% evaluated it as useful or very useful. During 2008 the figures were 89% and 79%. The students outlined that this assessment oriented their study, allowed them to discover their weaknesses and have a perception of the degree of difficulty of the final exam. Over 90% of students that took the formative evaluation, improved their academic achievement. CONCLUSIONS Formative assessments are well evaluated by medical students and improve their academic achievement.