Models are very important tools when learning and communicating about science. Models used in secondary school biology education range from concrete scale models, such as a model of a skeleton, to abstract concept-process models, such as a visualisation of meiosis. Understanding these concept-process models requires a profound understanding of the concept of models and how they are used in biology. This study evaluates an existing framework for its use in assessing students' understanding of biological concept-process models. Four additions were required to extend the applicability of the framework to concept-process models. We were also able to give an indication of students' current level of understanding of these models, showing room for improvement in all aspects of understanding. Since concept-process models have a central place in many scientific disciplines, it is important that students have a deep understanding of the nature, application and limitations of these models. The current study contributes to assessing the way students reason with concept-process models. Knowing how to improve students' view on the use of concept-process models in biology may lead to higher scientific literacy.