The effects of preharvest applications of pyrrolnitrin (a biologically derived fungicide) on postharvest longevity of `Bristol' black raspberry (Rubus occidentals L.) and `Heritage' red raspberry [R. idaeus L. var. strigosus (Michx.) Maxim] were evaluated at two storage temperatures. Preharvest fungicide treatments were 200 mg pyrrolnitrin/liter, a standard fungicide treatment (captan + benomyl or iprodione) or a distilled water control applied 1 day before first harvest. Black raspberries were stored at 18 or 0 ± lC in air or 20% CO2. Red raspberries were stored at the same temperatures in air only. Pyrrolnitrin-treated berries often had less gray mold (Botrytis cinerea Pers. ex Fr.) in storage than the control but more than berries treated with the standard fungicides. Storage in a modified atmosphere of 20% CO2 greatly improved postharvest quality of black raspberries at both storage temperatures by reducing gray mold development. The combination of standard fungicide or pyrrolnitrin, high CO2, and low temperature resulted in more than 2 weeks of storage with less than 5% disease on black raspberries; however, discoloration limited marketability after≈ 8 days under these conditions. Chemical names used: 3-chloro-4-(2'-nitro-3'-chlorophenyl) -pyrrole (pyrrolnitrin); N-trichloromethylthio-4-cyclohexene-l12-dicarboximide (captan); methyl 1-(butylcarbamoyl) -2-benzimidazolecarbamate) (benomyl); 3-(3,5 -dichlorophenyl) -N-(l-methylethyl -2,4-dioxo-l-imi-dazolidinecarboxamide (Rovral, iprodione).