A requirement for lineage analysis is tight temporal control of label induction. In the context of the tamoxifen-inducible cre/lox system, this means that there can be no residual tamoxifen to activate cre driven by promoters that might become upregulated over time or following injury. However, the protracted half-life of tamoxifen can allow recombination longer than generally appreciated. This protocol describes the appropriate “chase” times necessary to ensure accurate lineage analysis.