Obesity has become an international public health concern. In the United States, the rates of overweight and obesity have escalated dramatically in the last several decades. The health implications of obesity stem from its relationship with the development and progression of several health complications and diseases. Cardiovascular disease, which is the number one killer of women and men, is strongly influenced by obesity. The exact biological relationship between these two conditions is difficult to understand because several overlapping physiological systems and processes influence their development. One important component that affects obesity and cardiovascular disease is the sex of the individual. Although this basic biological variable is an obvious area for scientific study, research analyzing the influence of sex on obesity and cardiovascular disease is gravely lacking. The Society for Women's Health Research convened a workshop of obesity and cardiovascular disease experts in November 2005 to identify the gaps in scientific knowledge and crucial next steps in research related to sex differences in obesity and cardiovascular disease. This meeting report describes the workshop attendees' recommendations in detail.