This article presents a phenomenographic study that investigates students' approaches to achieving understanding. The results are based on interviews, addressing physiological phenomena, with 16 medical students in a problem-based curriculum. Four approaches--sifting, building, holding and moving--are outlined. The holding and moving approaches describe variations in deep-level processing. The moving approach is characterised by an intention to continuously refine understanding in an open-ended process. The student strives for a change in perspective and deliberately creates actions that are rich in variation and challenge. The holding approach is characterised by an intention to reach a final goal. This is achieved by high degrees of structure and control in the learning act. Understanding is sometimes sealed, "held on to" and can be threatened by new input and other students' viewpoints. The study also shows how students deal with details when constructing understanding of wholes. (Contains 4 tables.)