In this and the accompanying paper we demonstrate that certain prokaryotic mRNAs, when modified at their 5′-termini with a cap structure, are translated in a eukaryotic cell-free protein synthesising system as efficiently as, or more efficiently than, eukaryotic mRNAs. Apparently, the prokaryotic mRNA contains all the information necessary for efficient recognition and initiation by eukaryotic translational components, except for the cap structure.