Steriod hormones are involved in many physiological processes, including tissue-specific gene expression, homeostasis, and development. The chick oviduct represents an excellent system in which to study many of these events, as it is highly steriod responsive. Here, we report the cloning of chick HNF-3β from an oviduct cDNA library and its expression pattern in adult tissues and in the developing oviduct in response to estrogen treatment. Overall, cHNF-3β was expressed at high levels in the immature chick oviduct and lung and, to a lesser extent, in the liver, kidney, and muscle. This expression pattern is divergent from that of mammalian HNF-3β, which is not expressed in kidney or muscle. Furthermore, several lengths of cHNF-3β mRNA transcripts were detected that were expressed tissue specifically. Interestingly, cHNF-3β mRNA levels were differentially influenced by estrogen as a result of a post-transcriptional effect on the cHNF-3β message in some tissues. Finally, a role for cHNF-3β is proposed in the estrogen-stimulated differentiation and development of the oviduct, as cHNF-3β mRNA expression is induced in the early stages of oviduct development and declines as the animal becomes sexually mature.