As a part of the studies on the regulatory mechanism of gene expression by gibberellic acid, the effects fo GA_3 on the protein biosynthesis and phosphorylation in maize seedlings were investigated in the presence of actinomycin D. The activites of protein biosynthesis and phosphorylation in germination seeds treated with GA_3 were greater than these of the control at the 3-day point after germination. It is assumed that the enhancement of protein biosynthesis by GA_3 in the presence of actinomycin D is due to the effects of GA_3 on the translational processes in which protein is produced from the mRNA synthesized previously.