* This work was presented at the meeting of the So-ciety for Clinical Investigation, May 1, 1961, and has been published in abstract form (1, 2). The investigation was supported in part by Research Grant A-3892 from the National Institutes of Health and by the Medical Research Foundation of Texas. tWork done as an Established Investigator of the American Heart Association. hance markedly the synthesis of protein in slices of seminal vesicles from immature rats. Further-more, an examination of the biochemical reactions in the synthesis of protein has revealed that this effect of testosterone does not involve either amino acid synthesis or transport but is secondary to the enhancement of a specific step in protein syn-thesis, the conversion of soluble ribonucleic acidamino acid complexes to microsomal ribonucleoprotein.