By　using　the　upper-　and　lower-solution　Method　of　partial　functional　differential　equations　and　the　oscillation　theory　of　functional　differential　equation,　the　oscillation　of　a　Population　equation　with　diffusion　and　delay　is　studied　and　a　sufficient　condition　for　all　positive　solutions　of　the　equation　to　oscillate　about　the　positive　equilibrium　is　obtained.　Finally,　a　model　arising　from　ecology　is　given　to　illustrate　the　obtained　results　(C)　2009　Elsevier　Ltd.　All　rights　reserved.