dbTEST (http://www.bch.msu.edu/~zacharet/dbtest/) is a relational database of all genes currently known to be expressed in the murine testis, and has been used to select clones for construction of high density cDNA arrays for toxicogenomics. The NCBI UniGene, Jackson Laboratories Mouse Gene Expression (GXD), and National Library of Medicine (MEDLINE) databases were searched to identify genes expressed in mouse testis. As of build 79 of the UniGene database, 5409 genes are represented in dbTEST. 4722 (87%) were obtained from the UniGene database as clusters containing at least one EST sequenced in a library derived from murine testis. Analysis of the GXD and MEDLINE identified an additional 252 (5%) and 435 (8%) genes, respectively. In addition to identifying genes experimentally shown to be expressed in the murine testis, the search of the literature also identified genes known to be involved in testis function in other species. 35% of these were derived from mouse, 35% from rat, and 30% from human model systems. Gene expression analysis of 588 genes using a commercially available array identified 159 genes constitutively expressed in murine testis. Of these 159, 127 (80%) were already contained in dbTEST. The remaining 32 were added to the dbTEST, bringing the final total of known genes in dbTEST to 5441. This approach represents an inexpensive, efficient, and productive method for creating comprehensive cell type, tissue, or organism specific transcriptomes, and takes full advantage of the exhaustive cDNA sequencing efforts of other researchers.