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For recognition by the translational machinery, most eukaryotic cellular mRNAs have a 5′ cap structure [eg m 7 G (5′) ppp (5′) N]. We describe a translation enhancer sequence (3′ TE) located in the 3′‐untranslated region (UTR) of the genome of the PAV barley yellow dwarf virus (BYDV‐PAV) which stimulates translation from uncapped mRNA by 30‐to 100‐fold in vitro and in vivo to a level equal to that of efficient capped mRNAs. A four base duplication within the 3′ TE destroyed the stimulatory activity. Efficient translation was recovered by addition of a 5′ cap to this mRNA. Translation of both uncapped mRNA containing the 3′ TE in cis and capped mRNA lacking any BYDV‐PAV sequence was inhibited specifically by added 3′ TE RNA in trans. This inhibition was reversed by adding initiation factor 4F (eIF4F), suggesting that the 3′ TE, like the 5′ cap, mediates eIF4F‐dependent translation initiation …