Measuring reproductive health is problematic. Awareness of the problems needs to be raised both among those collecting and those using data on reproductive health. This paper discusses two major measurement questions - one related to ascertainment and the other to attribution. The first question is to what extent the observed levels and patterns of reproductive health outcomes in women are valid as opposed to artefacts of the data sources and the data collection methods? The second question is can lack of evidence of effectiveness for any reproductive health intervention ever confidently be separated into no effects vs an inability to measure effects? Determining the effectiveness of health interventions is notoriously difficult. Reproductive health may not be a case for special pleading in the competition for scarce resources, but equally it should not be a case for special standards of proof of the effectiveness of interventions - standards which have not indeed been met by many other, and yet unquestioned, health care priorities. "What works" in reproductive health should in fact be judged from at least four different perspectives: from that of women and their families, health professionals, the scientific community, and national and international policy-makers.