Technical Abstract: Background: The Arabidopsis ortholog of the 30 kD subunit of the mammalian Cleavage and Polyadenylation Specificity Factor (AtCPSF30) is an RNA-binding endonuclease that is associated with other Arabidopsis CPSF subunits (orthologs of the 160, 100, and 73 kD subunits of CPSF). In order to better understand the nature of complexes containing AtCPSF30, and to further explore the functions of the protein, the subcellular distribution of the protein was examined, using fusion proteins containing fluorescent reporters. Resuts: It was found that AtCPSF30 by itself localizes to distinctive cytoplasmic foci that are also the sites of accumulation of AtDcp2, a marker diagnostic of so-called RNA processing bodies. AtCPSF30 could be found in the nucleus when co-expressed with either of two other CPSF subunits (AtCPSF160 and AtCPSF73(I)). Interestingly, co-expression of AtCSPF30 with AtCPSF100 altered the location, not of AtCPSF30, but rather of AtCPSF100, with the two proteins residing in the cytoplasmic foci seen in cells expressing just AtCPSF30. Co-expression of AtCPSF30 and AtCPSF73(II) had no appreciable effects on the distribution of either protein. Conclusions: These results place AtCPSF30 within or near P-bodies in the cytoplasm, and suggest that a cytoplasmic CPSF complex may be involved in RNA movement and/or degradation in plants. They also suggest that the nuclear CPSF complex is a dynamic one, and that nuclear AtCPSF30 is not in direct physical contact with AtCPSF100.