Protein phosphatase 2A (PP2A) is one of the most abundant serine/threonine phosphatases, with a critical role in embryonic development and human disease. There are two isoforms of the catalytic subunit of PP2A, Ppp2ca and Ppp2cb. Null mutation of Ppp2ca leads to early embryonic lethality at E6.5, hindering functional study of PP2A beyond this stage. We generated conditional null alleles of Ppp2ca and Ppp2cb by flanking with loxP sites exons 3 to 5 of Ppp2ca and exon 3 of Ppp2cb. Ppp2cafl/fl mice did not display any visible phenotype. Homozygous mutants in which Cre-mediated excision resulted in global deletion of Ppp2ca displayed embryonic lethality and developmental defects similar to those previously reported. Ppp2cbΔ/Δ mice generated by the same strategy did not display any obvious morphological or physiological defects. These mouse strains can serve as important genetic tools to study the roles of PP2A during development and disease in a spatial- or temporal-specific manner. genesis 50:429–436, 2012. © 2011 Wiley Periodicals, Inc.