Summary: We report an improved vector, pCAGGS‐FLPe, for transient expression of the enhanced FLP recombinase in mouse ES cells and oocytes. In standard transfection experiments, about 6% of total ES colonies showed FLP recombination, albeit with mosaicism within each colony. After microinjection of pCAGGS‐FLPe into oocytes, about one‐third of heterozygotic mice born showed complete FLP recombination. Thus pCAGGS‐FLPe presents two practical options for removal of FRT cassettes in mice. genesis 31:6–10, 2001. © 2001 Wiley‐Liss, Inc.