Significant and rapid fertility declines have occurred in many countries in the poor world over the past decade; many of these were unanticipated by demographers. Despite advances in statistical technique and demographic theory, little is yet known about the demographic rhythms of life in poor countries, or of the social forces behind them. Fertility decline, however, appears to have much to do with changes, economic and otherwise, within the family structure. The impact of ‘family planning’ programmes on fertility decline appears to have been exaggerated. ‘Population planners’ should be sensitive to the fact that a decline in fertility does not necessarily mean that an improvement in the standard of living has occurred, and they should not assume that reducing fertility automatically increases either the quality of life or the prospects for ‘development’.