The 5' flanking region of human factor H was cloned using nested polymerase chain reaction (PCR) and the promoter finder method. A total of 1.2 kb has been sequenced and a number of putative regulatory elements identified including glucocorticoid response elements cAMP responsive element, HTF-1, and acute phase signal sequences. A 717 b.p. fragment was cloned into a CAT reporter vector and transfected into HeLa cells. A series of truncations from the 5' end of this fragment were also cloned into the CAT vector. Analysis of CAT activity of the cell lysates showed that the region from -699 to +18 is likely to contain promoter elements for the factor H gene as it was able to drive transcription of the CAT gene.