These transgenic mice express Cre recombinase under the direction of the Purkinje cell-specific L7/Pcp2 promoter. Recombinase activity is observed in most Purkinje cells and some retinal bipolar neurons. Small amounts of activity are observed in an unidentified population of cells of the central nervous system tissue. Recombination is first observed around postnatal day 6 and is fully established 2 to 3 weeks after birth.