The development of the central nervous system is known to require lineage-specific factors that are expressed in neuroblasts and their descendants, as well as molecules involved in cell-cell signaling mechanisms. The transcription factors encoded by the gooseberry locus appear to be required for the proper specification of neuroblasts and their lineages. To examine whether gooseberry expression is lineage-specific, we have utilized the FLP recombinase of yeast to positively mark cell lineages throughout Drosophila development. In this system, the actin5C promoter and the lacZ gene are separated by a polyadenylation signal flanked by two direct repeat FRTs. A heat shock is used to induce a pulse of FLP recombinase which catalyzes a site-specific recombination event between the FRT sites. The resulting excision of the polyadenylation site allows expression of lacZ from the actin5C promoter. The descendants of a cell which has undergone a recombination event are now positively marked, enabling us to compare cell lineages with the pattern of gooseberry gene expression. We find that the expression of the gooseberry locus is lineage-specific, suggesting that gooseberry may function as a selector gene in the patterning of the Drosophila central nervous system.