Male predominance in metopic and sagittal craniosynostosis and in nonsynostotic plagiocephaly suggests a role for circulating androgens in early craniofacial development. Androgens have been documented to play an important role in postnatal skeletal growth, and the androgen receptor has been recently demonstrated in human and rat osteoblast-like cell lines and in human long bones. The purpose of this study was to describe the expression of androgen receptor in the fetal craniofacial skeleton. The heads of E18 fetal CD-1 male and female mice were fixed in 10% formalin, decalcified, and embedded in paraffin. Four- to 6-mum coronal and sagittal sections were stained with a monoclonal antibody specific to androgen receptor, which was detected by an avidinbiotin conjugate and peroxidase system. The sections were then examined for androgen receptor expression patterns. Strong androgen receptor immunoreactivity was observed in the dura mater of developing fetuses. Androgen receptor expression was also noted in cells lining the osteogenic fronts and in calvarial osteoblasts. Similar androgen receptor expression patterns were found in male and female mice. Androgen receptor is abundantly expressed in fetal dura mater and calvarial bone. This study confirms the presence of androgen receptor in the murine fetal craniofacial skeleton, suggesting a potential role for the anabolic effects of androgens in the developing craniofacial skeleton.