To gain a more detailed understanding of health care utilization patterns, researchers have begun to disaggregate administrative data by a number of important variables, including sex. Our purpose in this article is to confirm the need for sex-disaggregated data in health research, but also to argue that the further step of gender-based analysis is necessary. We focus on a number of conceptual and methodological issues surrounding sex-disaggregated administrative data, and we conclude that sex disaggregation alone is insufficient. Gender-sensitive indicators must be developed and used in order to understand the context of health differences and develop appropriate policies and programs.