BACKGROUND There is a growing international commitment to universal health coverage (UHC), but limited means to determine progress towards that goal. We developed a practical index for capturing health service coverage - a critical dimension of UHC -- that was more inclusive than previous methods. METHODS Our data included publicly-available, indicators reflecting health service delivery, infrastructure, human resources, and health expenditures for 103 countries. We selected a set of internally-consistent indicators and performed principal component analysis. Multiple imputation was used to address missing values. We extracted and rotated four components related to health service coverage and developed a composite index for each country for 2009. RESULTS Explaining cumulatively almost 80% of the total variance, the four extracted components were characterized as: 1) provision of services, 2) infrastructure and human resources, 3) immunization (provision of services), and 4) financial resources. The health service coverage index developed from these components demonstrated strong correlation with health outcome measures such as infant mortality and life expectancy, supporting its validity. Index values also appeared generally consistent with published reports and the regional distribution of health coverage. CONCLUSIONS Our approach moved beyond common indicators of service coverage focused on infectious diseases and maternal and child health, to include information on necessary health inputs. The resulting, balanced, composite index of health service coverage demonstrated promise as a metric, likely to discriminate coverage levels between countries and regions. An important number of service provision indicators were correlated, therefore a reduced set of services performed well as a proxy for the full set of available indicators. This parsimonious index is a start toward simplifying the task of policy-makers monitoring progress on a key domain of universal health coverage.