PURPOSE Information about the patient's current drug list is a prerequisite for safe drug prescribing. The aim of this study was to explore general practitioners' (GPs) understandings of who is responsible for the patient's drug list so that drugs prescribed by different physicians do not interact negatively or even cause harm. The study also sought to clarify how this responsibility was managed. METHODS We conducted a descriptive qualitative study among 20 Swedish physicians. We recruited the informants purposively and captured their view on responsibility by semistructured interviews. Data were analyzed using a phenomenographic approach. RESULTS We found variation in understandings about who is responsible for the patient's drug list and, in particular, how the GPs use different strategies to manage this responsibility. Five categories emerged: (1) imposed responsibility, (2) responsible for own prescriptions, (3) responsible for all drugs, (4) different but shared responsibility, and (5) patient responsible for transferring drug information. The relation between categories is illustrated in an outcome space, which displays how the GPs reason in relation to managing drug lists. CONCLUSIONS The understanding of the GP's responsibility for the patient's drug list varied, which may be a threat to safe patient care. We propose that GPs are made aware of variations in understanding responsibility so that health care quality can be improved.