Polychlorinated biphenyls (PCB) are persistent environmental contaminants that have been reported to adversely affect reproduction in mammals. The exact mechanism of action of these chemicals on oocyte and embryo development are not known. Previous studies in our laboratory demonstrated that PCB adversely affect in vitro oocyte maturation and embryo development in two different in vitro systems (cattle, rabbit). The objective of present study was to investigate the possible role of the arylhydrocarbon receptor (AhR) in PCB toxicity. The AhR is a transcription factor activated by ligands such as dioxins or PCB. Its transcriptional activity depends on dimerisation with its nuclear partner ARNT. The presence of AhR and ARNT was investigated in bovine and rabbit genital tract (uterus, ovary) and embryonic tissues, employing RT-PCR and immunohistochemistry.