The goal of our work is to understand the molecular mechanisms that control eukaryotic mRNAs in the cytoplasm with a focus on control of translation and stability. Our major contributions have been as follows. First, we identified the major pathways of mRNA turnover in eukaryotes, which initiates with poly(A) tail shortening and then either triggers 3' to 5' degradation of the mRNA body, or decapping, leading to 5' to 3' exonucleolysis. Second, we identified many of the major nucleases of mRNA degradation and their regulators including the decapping enzyme, the 3' to 5' decay complexes, and the deadenylases. Third, we have provided evidence that decapping and translation initiation are in competition and that many of the factors promoting decapping do so by interfering with translation initiation. Finally, we have contributed to the identification of cytoplasmic mRNP granules containing non-translating mRNP (P-bodies and stress granules), and are studying their biological significance.