Sarco(endo)plasmic reticulum calcium ATPases (SERCA) are cellular pumps that transport Ca(2+) into the sarcoplasmic reticulum (SR). Serca2 is the most widely expressed gene family member. The very early embryonic lethality of Serca2(null) mouse embryos has precluded further evaluation of loss of Serca2 function in the context of organ physiology. We have generated mice carrying a conditional Serca2(flox) allele which allows disruption of the Serca2 gene in an organ-specific and/or inducible manner. The model was tested by mating Serca2(flox) mice with MLC-2v(wt/Cre) mice and with alphaMHC-Cre transgenic mice. In heterozygous Serca2(wt/flox)MLC-2v(wt/Cre) mice, the expression of SERCA2a and SERCA2b proteins were reduced in the heart and slow skeletal muscle, in accordance with the expression pattern of the MLC-2v gene. In Serca2(flox/flox) Tg(alphaMHC-Cre) embryos with early homozygous cardiac Serca2 disruption, normal embryonic development and yolk sac circulation was maintained up to at least embryonic stage E10.5. The Serca2(flox) mouse is the first murine conditional gene disruption model for the SERCA family of Ca(2+) ATPases, and should be a powerful tool for investigating specific physiological roles of SERCA2 function in a range of tissues and organs in vivo both in adult and embryonic stages.