World Bank Technical Paper No. 356. The fragmentation in African financial markets and its persistence despite reforms to liberalize those markets have been difficult to explain. This paper reports findings from surveys of formal and informal institutions and their clients in Ghana, Malawi, Nigeria, and Tanzania to test hypotheses explaining different aspects of fragmentation, which occurs when different market segments are poorly linked and interest rate differentials cannot be fully explained by differences in costs and risks. The study concludes that financial development strategies, and World Bank operations supporting them, should explicitly include informal and semi-formal financial institutions to improve the extent and efficiency of financial intermediation in the medium term.