The filamentous fungus Cunninghamella utilizes cytochrome P450 system(s) in the metabolism of a broad range of polyaromatic and aliphatic pollutants and a variety of drugs, but prior attempts at isolation of P450 system components of this fungus have been generally unsuccessful. We report upon the cytochrome P450 oxidoreductase (CPR) gene from two widely studied species, C. elegans and C. echinulata. The C. elegans CPR gene was obtained by screening a genomic library using as probe a PCR amplicon obtained with degenerate primers based on known CPRs. The 2420 bp coding region contained two apparent introns (149 bp and 138 bp). Northern blot analysis showed that the CPR gene is transcriptionally expressed in C. elegans and appears to be inducible by an alkane substrate, n-tetradecane. Phylogenetic comparison of the deduced C. elegans CPR (710 aa) suggested that it is more closely related to animal CPRs (41-42%) than to yeast (38-41%) and plant (35-36%) forms. A 2074 bp sequence containing most of the CPR gene homolog from C. echinulata was also isolated.