In order to identify cytochrome P450s that are expressed in porcine ovaries, the RT/PCR methodology was used with a set of primers that corresponds to two conserved regions of the 2C gene subfamily of these enzymes. Five independent cDNA clones were isolated from preovulatory follicles (PF1, PF11, PF13, PF14, PF15) and six from the corpus luteum (CL1, CL6, CL7, CL8, CL12, CL13). The structural identities categorize these 11 P450s into two groups, group A consisting of PF1, CL7 and CL8 and group B consisting of the remaining clones. In addition, segments that are apparently interchanged between the clones were also revealed, implicating gene conversion events that have homogenized the sequence of these P450s. Furthermore, although the larger group of these porcine enzymes (group B forms) are structurally very similar to the known human P450s of the 2C gene subfamily, the group A forms are much more distantly related, implying that the 2C P450s might have evolved differently in the two species.