In addition to the m7G cap structure, the length of the 5' UTR and the position and context of the AUG initiator codon (which have been discussed elsewhere in this volume), higher order structures within mRNA represent a critical parameter for translation. The role of RNA structure in translation initiation will be considered primarily, although structural elements have also been found to affect translation elongation and termination. We will first describe the different effects of higher order RNA structures per se, and then consider specific examples of RNA structural elements which control translation initiation by providing binding sites for regulatory proteins.