The two proteins of molecular weights 150,000 and 195,000 specific of turnip yellow mosaic virus (TYMV) RNA translation in reticulocyte lysates have now also been detected in two other cell-free systems programmed with TYMV RNA: the wheat germ extract and the Ehrlich ascites cell-free system. The wheat germ extract contains proteases that affect the nascent TYMV polypeptide chains. The specific post-translational maturation of the protein of molecular weight 195,000 known to occur in the reticulocyte lysate has been investigated in the ascites system. An N-terminal fragment and a C-terminal fragment of molecular weights 120,000 and 78,000, respectively, could be detected co-migrating with the post-translational cleavage products observed in the reticulocyte lysate. Similarly, a C-terminally labelled 78,000 molecular weight fragment could be observed in the wheat germ system. The differences between the three in vitro systems with respect to TYMV RNA translation are discussed.