The anterior lobe of the pituitary gland is composed of five hormone-producing cell types and develops from Rathke's pouch, an invagination of oral ectoderm. In mice, rapid cell proliferation occurs in the pouch from embryonic day 12.5 (e12.5) to e14.5, preceding the appearance of most hormone transcripts. Cell-type-specific commitment probably occurs prior to e14.5, but cell differentiation can be demonstrated only by detection of hormone transcripts. Although several transcription factors critical for pouch expansion are known, few of their target genes have been identified. To identify putative transcription factor target genes and cell-type-specific markers, we used differential display PCR analysis of RNA prepared from e12.5 and e14.5 Rathke's pouches. We present an expression profile of the developing pituitary gland including 83 transcripts, 40% of which are novel. The tissue distribution, cell specificity, and developmental regulation were determined for a subset of the transcripts.