Abstract: The cowpea is a very important legume for peasant farmers in West Africa but this crop is very sensitive to bruchid attacks during storage. A study was carried out in a sub humid zone of Burkina Faso to determine the relation between the dynamic of bruchid and parasitoid populations in the fields and cowpea infestation at harvest. The variations in insect numbers were weekly estimated by net captures during the growth of an early and a late cowpea variety. Adults of two bruchid species, Callosobruchus maculatus (Fab.). and Bruchidius atrolineatus (Pic) appeared early in the fields before cowpea flowering and their population regularly increased over time and from early to late cowpea variety. The Pteromalid Dinarmus basalis Rond was the only larval parasitoid encountered. Its adults appeared later than bruchids and their parasitism activity increased over time. At harvest, 35% of the early cowpea pods and 74.5% of the late cowpea pods were infested by bruchid eggs. 58.5 and 72% of the bruchid eggs laid respectively on the early and the late cowpea variety were parasitized by Uscana sp. The level of cowpea seed infestation by bruchids at the beginning of storage was estimated to be 1 and 2.7% for the early and late cowpea variety respectively. The parasitism rate of bruchid larvae by D. basalis was estimated at this period to be 7.8% for early cowpea variety and 18.2% for the late variety. These results are discussed in view of developing an integrated control method based on the enhancement of the pest natural enemies in the fields and/or into storage systems in combination with beneficial farming practices.