The processing of yam into dehydrated chips is used extensively in certain areas of West Africa to stabilize the product. However, the chips are often severely attacked by borers, which can reduce whole stocks to powder within a few months. The level of protection provided by various biological productstierived from neem (Azadirachta indica) and Crotalaria caricea was compared with that of a synthetic pesticide, SofagrainTM (1.5% deltamethrin + 0.5% pirimiphos-methyl), a reference chemical for stored products in Benin. Insect damage was assessed over a period of 10 months in the store room. Infestation was well controlled by all treatments for up to six months, after which only Sofagrain provided any protection. After 10 months, the chemical still provided a good level of protection, whereas the untreated control was severely attacked by the following insects: Dinoderus porcellus and D. bifoveolatus, Rhyzopertha dominica, Lasioderma serricorne, Palorus subdepressus and Tribolium castaneum. L. serricorne was the most abundant pest, followed by P. subdepressus and T. castaneum. Among the biological products used, the three neem-based treatments (oil, seed powder and leaf powder) gave the best level of protection, whilst Crotalaria seeds and periodic turning over of storage bags had little effect on reducing damage.