A systematic literature review of research on midwifery care of poor and vulnerable women from 1925 to 2003, which included topics studied, research methods used, and special issues and implications for future research, was performed; 44 studies published between 1955 and 2003 were identified. The majority were retrospective, descriptive studies. Outcomes examined included prenatal care visits, vaginal versus operative births, labor interventions, maternal and neonatal mortality and morbidity, birth weight, and cost-effectiveness. Studies showed that midwives predominantly serve vulnerable women who are young, poor, immigrants, or members of racial and ethnic minorities. Preterm birth prevention is emerging as a midwifery research focus. Health system changes are making it more difficult to provide effective care and counseling to disadvantaged women, especially in managed care settings. Extensive evidence documents excellent outcomes of midwifery care for the poor in urban and rural settings over the past three quarters of a century. Future research should include more intervention studies and use both qualitative and quantitative methods to investigate midwifery processes of care and the process-outcome connection. The research focus should broaden beyond childbirth to include gynecology, family planning, and primary care issues. Health disparities, cultural studies, obstetric interventions, and poor women's experiences of childbirth and midwifery care are important topics for future research.