The Prevention of Maternal Mortality Program is a collaborative effort of Columbia University's Center for Population and Family Health and multidisciplinary teams of researchers from Ghana, Nigeria and Sierra Leone. Program goals include dissemination of information to those concerned with preventing maternal deaths. This review, which presents findings from a broad body of research, is part of that activity. While there are numerous factors that contribute to maternal mortality, we focus on those that affect the interval between the onset of obstetric complication and its outcome. If prompt, adequate treatment is provided, the outcome will usually be satisfactory; therefore, the outcome is most adversely affected by delayed treatment. We examine research on the factors that: (1) delay the decision to seek care; (2) delay arrival at a health facility; and (3) delay the provision of adequate care. The literature clearly indicates that while distance and cost are major obstacles in the decision to seek care, the relationships are not simple. There is evidence that people often consider the quality of care more important than cost. These three factors--distance, cost and quality--alone do not give a full understanding of decision-making process. Their salience as obstacles is ultimately defined by illness-related factors, such as severity. Differential use of health services is also shaped by such variables as gender and socioeconomic status. Patients who make a timely decision to seek care can still experience delay, because the accessibility of health services is an acute problem in the developing world. In rural areas, a woman with an obstetric emergency may find the closest facility equipped only for basic treatments and education, and she may have no way to reach a regional center where resources exist. Finally, arriving at the facility may not lead to the immediate commencement of treatment. Shortages of qualified staff, essential drugs and supplies, coupled with administrative delays and clinical mismanagement, become documentable contributors to maternal deaths. Findings from the literature review are discussed in light of their implications for programs. Options for health programs are offered and examples of efforts to reduce maternal deaths are presented, with an emphasis on strategies to mobilize and adapt existing resources.