Little is known about the relationship of demographic, health, and psychosocial factors with health services utilization over time among low-income female heads of household. In a case-control study conducted between 1991 and 1997, 273 homeless and low-income housed mothers living in Worcester, Massachusetts were interviewed at baseline and at a two-year follow-up. The use of outpatient and emergency department care in this study sample was examined. High usage patterns were found at baseline. At the two-year follow-up, poor health status, non-White race, and fewer supportive relationships were significantly associated with frequent emergency department visits. Women with higher rates of ongoing outpatient medical care visits were more likely to have fewer social supports and more bodily pain than women with lower rates of ambulatory care usage. Mental health and victimization were not associated with service use patterns. In order to address poor women's needs in a more effective and potentially less costly way, health programs must understand their need for social support and culturally responsive services.