Quality of care can be measured by using either processes or outcomes. Each method has its strengths and limitations. With the concurrence of the Assessing Care of Vulnerable Elders (ACOVE) Policy Advisory Committee, we chose to assess the care of vulnerable elders by using processes rather than outcomes. We did so because processes are a more efficient measure of quality; for most conditions there are insufficient information in the medical record and a paucity of validated models to adequately adjust outcomes for differences in case mix between providers; and ultimately, processes of care are amenable to direct action by providers. To be a valid measure of quality, a health care process must be strongly linked to an outcome that is important to patients. Ideally, high-quality published studies would link performance of all such processes to outcomes; however, few health care processes are supported by high-quality evidence. Even when a process is supported by strong evidence from randomized clinical trials, the inclusion and exclusion criteria of the clinical trials leave the evidence directly applicable to only a narrow group of patients. This is particularly true for vulnerable elders, who are typically excluded from clinical trials. Therefore, as we developed the ACOVE quality indicators, we used expert opinion to interpret the available evidence for applicability to vulnerable elders. Our methods entailed a literature review and several levels of expert opinion, which we explain in detail.