Abstract: The dimorphic transition of yeast to the hyphal form is regulated by the mitogen-activated protein kinase (MAPK) and cAMP-dependent protein kinase A (PKA) pathways in Saccharomyces cerevisiae. Signaling pathway-responsive transcription factors such as Ste12, Tec1, and Flo8 are known to mediate filamentation-specific transcription. We were interested in investigating the translational regulation of specific mRNAs during the yeast-to-hyphal transition. Using polyribosome fractionation and RT-PCR analysis, we identified STE12, GPA2, and CLN1 as translation regulation target genes during filamentous growth. The transcript levels for these genes did not change, but their mRNAs were preferentially associated with polyribosomes during the hyphal transition. The intracellular levels of Ste12, Gpa2 and Cln1 proteins increased under hyphal growth conditions. The increase in Ste12 protein level was partially blocked by mutations in the CAF20 and DHH1genes, which encode an eIF4E-inhibitor and a decapping activator, respectively. In addition, the caf20 or dhh1 mutations showed defects in filamentous growth. The filamentation defects of caf20 or dhh1mutations were suppressed by the STE12 overexpression. These results suggest that Caf20 and Dhh1 control yeast filamentation by regulating STE12 translation.