Data on health care utilization are used to address important questions about what is done for whom, and can shed light on why and with what outcome, in the large segment of economic life that “delivers” health care services to populations. We describe the purposes of and major issues associated with common study types (e.g. small area variations, disparities, provider profiling, cost effectiveness). Methodologic issues include: defining the study scope in accordance with its purpose (data source, population, timeframe, units of analysis and units of inference); choosing appropriate models (dealing with clustered observations, skewness, heteroscedasticity, and “point masses” at zero); and addressing the “censoring” effect of death on cost.