To achieve the goal of personalized medicine, we must first improve our understanding of the differences in health and illness between men and women. The purpose of the Illinois Women's Health Registry (USA) is to provide a research and education tool that advances scientific knowledge of sex- and gender-based differences in health and disease. Specifically, the Registry is a confidential 30-min health and lifestyle survey for female residents of Illinois over the age of 18 years. The survey includes questions regarding health, environment, health-related behaviors, symptoms and illnesses or conditions that a participant may have now or has had in the past. By enrolling in the Registry, women throughout the state are provided with information and access to clinical research studies that they may be eligible for, based on their self-reported health information. The Registry not only serves as a platform for recruitment into pivotal research studies, but also represents the beginning of a state-wide database that enables researchers to examine the collective de-identified health information provided by women living in Illinois. Ultimately, a cross-sectional and longitudinal analysis of these data will help to clarify the issues that women themselves identify as their main health concerns. In response to these concerns, specific research studies can be designed and launched, allowing us to eventually deliver tailored treatment and prevention options to women. Finally, by creating a reliable state-focused research tool, developed by staff that are trained in women's health research, we can compare health issues across the state and apply strategies for improvement where it is needed most. This article will provide examples of sex differences in disease, the lack of federal enforcement for inclusion of women in studies, researcher-perceived burdens and sex-based reasons as to why recruitment of women is considered to be more challenging. In addition, this article will discuss what a women's health registry is and why we need one in Illinois, how we have recruited women and our successes and challenges. Our goal is to inform the reader about the utility of a state-based tool and to provide a discussion regarding the lessons learned in order to aid other states in implementing this kind of program.