Total RNA, polyribosomes and polyribosomal RNA have been isolated from immature wheat grain and used to prime the wheat-germ cell-free protein synthesis system to produce storage protein. The synthesis of wheat prolamins, a major fraction of storage proteins, was mainly associated with membrane-bound polyribosomes. The ratio of bound to free polyribosomes increased from one at 8 days to approximately three at 32 days post-anthesis. SDS polyacrylamide gel electrophoresis and fluorography of the prolamins showed that the same components were being synthesized and accumulated from 12 days post-anthesis onward. Evidence is presented that prolamins within the molecular weight range 35 000-45 000 may be translated with a signal sequence attached. These signal sequences are rapidly removed during translation and further post-translational modifications may occur over longer periods.