This chapter describes procedures for an enhancer trap screen, using P-element vectors containing lacZ fusion genes, to isolate genes involved during Drosophila neurogenesis. The ability of the enhancer trap method to reveal the expression pattern of a gene should greatly facilitate the identification of a number of genes operating in any neural developmental process, regardless of their function at earlier stages or in other tissues. This method should complement genetic screens for mutant phenotypes and allow the isolation of genes that would stay undetected in standard genetic saturation screens. The chapter describes a screening method based on the assumption that some of the genes involved in the specification of individual cell fates during neurogenesis would be expressed in a restricted subset of cells. The expression patterns of the svp and sea genes that have been identified in such a screen are very similar to those of the lacZ reporter gene in the respective transformant lines, confirming the utility of this approach to identify genes expressed in spatially restricted patterns during nervous system development.