The 6-kb human keratin 5 (KRT5) promoter drives a cre/ERT2 cassette. The cre/ERT2 is flanked by an intron and a polyadenylation sequence from the pCI mammalian expression vector. The construct was injected into fertilized zygotes. 11 founder lines were obtained, and 1 line that gave robust recombination in tracheal basal cells was propagated and maintained on a C57BL/6 x C3H background. (J:152012)