Medical providers often have a significant influence on treatment decisions which they can use in their own financial interest. Classical models of supplier-induced demand predict that medical providers will supply fewer services if they face increasing prices. We test this prediction based on a reform of hospital financing in Germany. Uniquely, this reform changed the overall level of reimbursement – with increasing prices for some hospitals and decreasing prices for others – without affecting the relative prices for different types of patients. Based on administrative data, we find that hospitals do indeed react to increasing prices by reducing service supply.