This paper, firstly, takes advantage of the principal component analysis to build a synthetic financial development indicator for every state member of the West Africa Economic and Monetary Union (WAEMU). Secondly, it examines empirically the link between financial development and economic growth, on the one hand, and the link between financial development and sectoral activities, on the other hand, over the period 1961-2005. To this end, it performs cointegration and Granger causality tests. The results show the existence of a stable long-run relationship between financial development and economic growth in WAEMU countries. The causality is either unidirectional, running from finance to economic growth, in 3 countries out of 8, and in 5 countries out of 8 the causality is bidirectional. Furthermore, at a sectoral level, results reveal some cases of unidirectional causality, running from finance to economic sector activities, and some cases of bidirectional causality. However, there are many cases of non-cointegration and non-causality between financial development and the agricultural sector. This may suggest that the financial sector does not drain sufficient amount of fund to the agricultural sector in order to favour its development.