A fertilized one-celled embryo contains all the genetic information to form the tissues and cells of the entire organism. Each division of the embryo results in a more restricted potential and a more specialized possibility for each of the two daughter cells to form a set of tissues and cells. In C. elegans, there are notably several master regulators of key cell fate decisions that have been well studied such as the Notch gene, lin-12, which for example, regulates the AC-VU decision to produce a wild-type vulva. More commonly, multiple genes act together in a combinatorial fashion to regulate the expression of a tissue or cell-type. In C. elegans, the gonad comprises two reflexed arms, each of which is mostly encircled by the gonadal sheath, a tissue composed of five pairs of cells. Gonadal sheath pair (Sh) 1 is necessary for maintaining the mitotically dividing stem cell population of the germline while Sh4 and Sh5 are necessary for ovulation of the mature oocytes into the spermatheca. Loss of the sheath results in extremely reduced fertility: at most one – two progeny per hermaphrodite. Because of its simple structure we have used the gonadal sheath as a model to examine the genes that are required for establishment and maintenance of tissue identity. We approached our goal in several ways. First, using an RNAi screen to look for genes that were necessary for the presence or maintenance of the gonadal sheath, we uncovered approximately 40 candidate genes. Only one of these had been previously localized to the sheath. Next, approximately one-half of these candidate gene products are predicted to interact with gene products that have predicted or been shown to localize to the gonadal sheath. Finally, we used a datamining approach to look at unique expression patterns that have been reported in the literature. Approximately 246 genes have been reported to localize to or affect the gonadal sheath. After checking the literature and databases, only the localization pattern of 88 of the 246 genes could be confirmed in the literature and databases. Twenty-eight of those genes were not ubiquitously expressed in all five sheath pairs but had unique sheath pair expression patterns. Taken together, these data reveal potential new relationships of combinatorial gene expression patterns that begin to uncover signals that mark the identity of the gonadal sheath.