Significant progress has been made over the past few decades in providing health care to populations in developing countries. According to the World Bank, the single most important obstacle the poor face in gaining access to health services remains the lack of physical infrastructure. Distance limits women's willingness and ability to seek care, particularly when appropriate transportation is in limited supply, communications difficult, and terrain and climate inhospitable. Constraints related to the availability of health personnel stem as much from their inefficient use within the health care system as they do from inadequate numbers and inequitable distribution. It is clear that the gains that have been made in enhancing health service availability over the past few decades are being eroded by the impact of economic crises and structural-adjustment programs. The evidence on the effect of costs on demand for health care is mixed, showing demand to be uninfluenced, negatively influenced, and even positively influenced by cost levels.