This study applies a multi-regional general equilibrium analysis to evaluate the economic impact of transgenic (Bt) cotton adoption in West and Central Africa (WCA). A special feature of the analysis was the careful estimation of productivity gains from Bt cotton adoption using several farm-level impact studies and a 2001 multi-country cost of production survey for cotton by the International Cotton Advisory Council. Two no-adoption scenarios for WCA (with cotton productivity loss from recent trends and without) are contrasted with a partial Bt cotton adoption case, under an international environment where Bt cotton is also adopted elsewhere. The analysis shows that under the no Bt cotton adoption and current declining productivity trends, the cotton sector in WCA shows lower output and declining export shares compared to other regions. Even without TFP loss, the pesticide-based cotton production system also results in eroding performance as other Bt adopting countries perform better and improve their world market positions. When WCA adopts Bt cotton, the cotton sector performs substantially better compared to the status quo and compares favorably with other regions.