We surveyed approximately 850 physicians in eight surgical specialties to investigate physicians' work in performing invasive services. Building on our analysis of physician work, we developed a relative value scale of physicians' services based on resource costs. First, we found that physician charges are not set in proportion to the resources required to perform a given procedure: there is a threefold variation, across hospital-based invasive procedures, in the ratio of charges to resource-based relative values. Second, for most procedures, the preoperative and postoperative periods represent 60% to 75% of a physician's total service time, but only 35% to 50% of the total service work. Lastly, intraoperative work per unit of time varies greatly. Work per minute for invasive procedures is two to three times that of medical office visits and is strikingly greater for some specialties. The Resource-Based Relative Value Scale, at a minimum, represents a useful tool for payers to identify procedures with potentially aberrant charges and also offers unique insights into the nature of physicians' work.