The Life After Cancer Epidemiology (LACE) Study, a cohort of 2321 early stage breast cancer survivors, was established in 2000 to examine how modifiable behavioral risk factors affect quality of life and long-term survival. Women were recruited primarily from the Kaiser Permanente Northern California Cancer Registry (KPNCAL) and the Utah cancer registry (UCR), United States. Baseline data were collected, on average, at two years post-diagnosis through self-administered questionnaires that included information on demographics, medical history, anthropometry, diet, supplements, physical activity and quality of life. The purpose of this paper is to describe the creation and baseline characteristics of the cohort. Forty-six percent of women to whom questionnaires were mailed agreed to participate. The cohort which is 80% white, was diagnosed predominantly with Stage I and II breast cancer (93%), and will have been followed for 5.6 years post-diagnosis, on average, by the end of 2004. Women reported slightly over four daily servings of fruit and vegetables, well below the suggested 5-A-Day national guidelines. Compared to women free of cancer, physical activity patterns were similar, while weight gain, especially in younger women, was higher than is typical. These data suggest that in the early years post-diagnosis, breast cancer survivors exhibit similar patterns to the general population in many health behaviors.