At least 34 complex I subunits of the electron transport chain are encoded by the nuclear genome, but only 14 of these have been mapped in the human. To rapidly map additional subunits, we have performed a combination of database mining and direct "wet" experimentation to identify intron and/or 5' upstream genomic DNA regions for 16 complex I genes. Wet experimentation was applied to 5 genes, and involved direct PCR amplification of introns by inter-exon PCR or splinkerette based PCR walking. Database mining was applied to 11 genes, and entailed the identification of incompletely spliced mRNAs and genomic CpG island clone sequences. This data was in files that carried no documentary description of the non-exon regions. Non-exon sequences were thus derived for 15 complex I genes and used to design functional gene specific PCR assays. Radiation hybrid mapping of these PCRs located 15 complex I genes to chromosomes l, 4, 5 (2 genes), 7 (2 genes), 8, 9 (2 genes), 11, 14, 16 (2 genes), 18, and 19.