During the development of Drosophila melanogaster the expression of glucose dehydrogenase (GLD) changes from non sex-limited to male limited. We have isolated the Gld gene and three other functionally related genes in the eclosion gene cluster by the method of chromosome walking. The Gld gene has been identified by two deletions and a translocation which genetically define the gene. A 2.8-kb RNA has been identified as the putative GLD mRNA. The temporal and spatial expression of this RNA is correlated with the expression of the GLD enzyme and levels of the steroid hormone ecdysterone. Using single-strand antisense probes we have detected three RNA species. However these three transcripts are not derived from the Gld locus. One of these RNAs is weakly detected by the multiple cloning site of the pSP65 vector. The level of detection of this latter RNA is greatly increased by the insertion of a specific Gld gene fragment in the pSP65 vector.