Using the enhancer trap approach we have searched for genes with important functions in oogenesis. We selected a line of flies with a P insertion, carrying the Escherichia coli lac Z gene, which showed beta-galactosidase expression in the nurse cell nuclei during oogenesis. Surrounding the P insertion we discovered a cluster of transcription units with enriched expression in the ovary. One of these encodes a protein with extensive sequence similarity to the human and yeast ubiquitin carboxyl terminal hydrolase. Analysis of a fusion protein including the putative ubiquitin carboxyl terminal hydrolase indicated that this protein does have the appropriate enzyme activity, and the gene was assigned the name ubiquitin carboxyl terminal hydrolase uch-D. The expression of this gene is enriched in the nurse cells and transcripts are transported to the embryo. Transcripts are abundant for the first few hours of development. The transcripts are found to be enriched on the ventral side of the oocyte and nurse cells. Rather little is known about the ubiquitin pathway in Drosophila and the discovery of this gene enables us to make predictions as to the roles it may play during early embryogenesis.