Chromosomal localization of three human cytochrome P450 genes belonging to the CYP2C subfamily (CYP2C8, 2C9, and 2C10) was identified by fluorescence in situ hybridization (FISH). An original MP-8 clone was used as a DNA probe for the assignment of the CYP2C10 gene, while two cDNA probes, a 1.37 kb fragment of CYP2C8 and a 1.19 kb fragment of CYP2C9, were obtained after amplifying the predicted fragments (MP-20 and MP-4 clones, respectively) by polymerase chain reaction using a single human liver cDNA library. The results showed that three human CYP2C8, 2C9, and 2C10 cDNAs were located at the same subchromosomal region, 10q24.1.