Polyethylene-lined bags of cornmeal stacked on pallets, both with and without deck sheets, were totally enclosed with a heat- shrunk polyethylene film and fumigated with phosphine and methyl bromide under a polyethylene tarpaulin. The deck sheets and polyethylene liners in the bags retarded the rate of penetration and the dissipation of the phosphine into and out of the cornmeal. However, phosphine concentrations in the bags were adequate to kill insects. Fumigation by placing phosphine pellets directly under the shrink-wrap produced erratic results. Polyethylene deck sheets between the pallet and bags greatly decreased the quantity of methyl bromide that reached the bags on shrink-wrapped pallets fumigated under a tarpaulin. It is doubtful that enough methyl bromide penetrated the bags on pallets with deck sheets to kill insects. Methyl bromide dissipated from under the shrink-wraps very rapidly, but concentrations inside the bags dissipated more slowly.