The factor H family of genes has been localised to human chromosome 1q32. This region encodes various proteins involved in complement regulation and is known as the regulators of complement activation (RCA) gene cluster. The factor H genes encode seven known plasma proteins. Using fluorescence in situ hybridisation (FISH), radiation hybrid (RH) mapping and BLAST alignment analysis, we have established that the factor H-related 5 (FHR-5) gene is closely linked to the other factor H gene family members. Analysis of the genomic sequence indicates that the FHR-5 gene is situated between FHR-2 and the non-complement protein factor XIIIb (Fl3B). Like all members of the factor H family. transcription of FHR-5 is in the telomeric direction. Furthermore, the short consensus repeats (SCRs) of FHR-5 are encoded by individual exons and splicing is of type 1. These data allow the generation of a more complete map of the factor H gene family.