Following the US experience, activity-based funding has become the most common mechanism for reimbursing hospitals in Europe. Focusing on five European countries (England, Finland, France, Germany and Ireland), this paper reviews the motivation for introducing activity-based funding, together with the empirical evidence available to assess the impact of implementation. Despite differences in the prevailing approaches to reimbursement, the five countries shared several common objectives, albeit with different emphasis, in moving to activity-based funding during the 1990s and 2000s. These include increasing efficiency, improving quality of care and enhancing transparency. There is substantial cross-country variation in how activity-based funding has been implemented and developed. In Finland and Ireland, for instance, activity-based funding is principally used to determine hospital budgets, whereas the models adopted in the other three countries are more similar to the US approach. Assessing the impact of activity-based funding is complicated by a shortage of rigorous empirical evaluations. What evidence is currently available, though, suggests that the introduction of activity-based funding has been associated with an increase in activity, a decline in length of stay and/or a reduction in the rate of growth in hospital expenditure in most of the countries under consideration.