This paper introduces a new quantitative approach to evaluating the delivery of public services. The paper combines a general discussion of the main features, strengths, limitations, and potential uses of tracing studies and Quantitative Service Delivery Surveys (QSDSs) with insights from past and ongoing applications of these tools. The paper is intended to stimulate discussion and to serve as a guide to those who want to do work in this field. The second part of the paper contains an empirical application of the QSDS approach to evaluate costs, quality, and incentives in the primary health care system. The emphasis is on the process of survey design and implementation. The paper warns that unless carefully planned, surveys of service delivery can easily fall prey to the very same problems, which they set out to measure. The key lesson to draw from this paper is that QSDSs and tracing studies require considerable time, commitment, and adequate funding, as well as careful consensus-building among in-country stakeholders.