In theory, and to some extent in practice, a free medical market has built-in financial incentives. Doctors operate on a fee-for-service basis in a system more or less conforming to the dynamics of supply and demand. The two gauges of the specialist's market value, and hence the fees he can command, are his popularity with patients and the respect of referring colleagues. Medical incomes are therefore unequal, and material and professional suc­ cess tend to develop hand in hand. A salaried service is based on different criteria, on peer or employer judgment rather than on consumer demand; payment for time replaces payment for work done. Under a nationalized system the two methods had to be reconciled.