In Drosophila, the three yolk protein (yp) genes are transcribed in a sex-, tissue- and developmentally specific manner, providing an ideal system in which to investigate the factors involved in their regulation. This project involved an analysis of the yolk protein 3 (yp3) gene and its flanking sequences in order to locate cis-acting DNA sequences necessary for the highly specific pattern of expression which, in the longer term, could be used to isolate the proteins interacting with them. Using P-element mediated germ-line transformation, it was demonstrated that a 747 bp promoter region was sufficient to direct sex-specific expression in the female fat body and both the temporal- and cell-type-specificity of expression during oogenesis. Further analysis of this region separated two elements capable of independently governing yp3 transcription in these tissues and a sub-fragment from the region conferring ovarian expression was used in gel retardation assays to demonstrate the presence of putative trans-acting proteins in ovarian nuclear extracts. No other sequences in the upstream, downstream or coding regions were identified that were autonomously involved in yp3 expression. Since yolk protein expression was known to be under nutritional and hormonal regulation, the in vivo influence of the steroid hormones, ecdysone and juvenile hormone on isolated regions of yp3 was also investigated. Finally, because the yolk protein genes are coordinately transcribed, the mechanisms and factors involved are expected to be the same for all three genes, and the results of this research are thus compared with those reported for yp1 and yp2 in an attempt to clarify current knowledge on the transcriptional control of this small gene family.