Available literature provides little insight into medical doctors' prescription choices when they are required to make complex trade-offs between different concerns such as treatment effect, costs, and patient preferences simultaneously. This study investigates this issue. It is based on a Discrete Choice Experiment (DCE) conducted with 571 Norwegian doctors, where the DCE captures preferences for medications described along five dimensions important for both clinical decision-making and prioritisation in the health sector. Although effectiveness is the most important determinant of choice in our study, doctors also put considerable weight on patients' preferences and on avoiding high total costs. The probability of choosing a particular medication increases when doctors have a positive experience with the medication. GPs value high clinical effectiveness less than hospital consultants do. They are also less concerned with patient preferences. For both groups of doctors it turns out that they are willing to make difficult trade-offs between attributes they are often assumed not to be willing to compromise on, like effectiveness or patient preferences, and cost measures - given that they have proper information about these attributes.