Mice expressing cre ubiquitously were generated by microinjecting linearized plasmid pBS185 DNA containing the cre recombinase gene under control of the human cytomegalovirus promoter into male pronuclei of (CBA x C57BL/6)F1 embryos. Several founders were generated, with two showing a high gene/locus deletion rate when crossed to floxed animals. (J:118712)