Objective Protein serine/threonine phosphatase-2A (PP-2A) is one of the most important phosphatases in eukaryotes. To lay down a basis for exploring its physiological functions in mammals, we have analyzed the expression patterns and distribution of the catalytic subunits for PP-2A in the different organs of 6 adult mice. Methods RT-PCR，Western blotting analysis and immunofluorescence histochemistry were used to establish the expression patterns and distribution in various tissues of the adult mouse. Results RT-PCR revealed that the PP-2Ac mRNAs were expressed at the highest levels in the brain, at reduced levels in the ovary, at much reduced levels in the muscle, kidney, spleen, heart, liver, lung and breast, at the lowest levels in the stomach. Western blotting analysis demonstrated that the highest protein expression level of the PP-2Ac proteins was also detected in the brain. A reduced level of this protein was found in the ovary, spleen, heart, liver and lung. A much reduced PP-2Ac protein expression level was detected in the muscle, kidney and breast. And the lowest expression level of PP-2Ac was detected in the stomach.Immunohistochemistry analysis revealed the specificity of PP-2Ac distribution at both cellular levels and tissue levels. Conclusion Our results suggest that PP-2A is one of the most important protein phosphatases in mammalians.