This study investigated the beliefs and practices of university lecturers around assessment theories and their links with teaching practices. Given the discrepancies in the literature, the research explored the gap in theoretical understandings of summative and formative assessment and the relationship between them, as well as the relationship with lecturers' own practices. In total, 109 lecturers from a Colombian institution of higher education participated. An instrument consisting mainly of quantitative questions, with some qualitative questions, which was originally designed to investigate these beliefs and practices among higher education lecturers in England, was used. The translation, validation and reliability processes of the instrument were carried out. Thus, an exploratory factorial study was performed to establish the dimensions of the instrument, determining seven factors. The results indicate discrepancies between what lecturers understand by formative and summative assessment and their practices in the classroom. This coincides with the theoretical contradictions also found in the analysis of specialised literature. It is concluded that a detailed understanding of the discrepancies between beliefs and practices would be valuable in redesigning the ways in which the training of lecturers' assessment competencies is approached.