The human UFD1L and CDC45L genes, adjacently located in the head-to-head direction on chromosome 22q11, are separated by a 884 base-pair (bp) segment constituting the putative transcriptional control region, In this region we mapped one transcription start site at 69 bp upstream of UFD1L gene, and one major and one minor start sites at 76 bp and 503 bp upstream of CDC45L gene, which are to center in the putative core promoters designated as P-UFD1L, P-CDC45L/major, and P-CDC45L/minor, respectively. The three core promoters lacked a TATA-motif and had a high GC-content. To determine the approximate ranges for the regulatory promoters, the 884-bp fragment or those with a series of deletions were placed between firefly and renilla luciferase genes present in the head-to-head direction in a single plasmid, and the resulting plasmids were assayed for the two transiently induced enzyme activities. The P-UFD1L and P-CDC45L/major regulatory promoters were within 418 and 454 bp upstream of the respective start sites and their greater parts were not overlapping. The activity of P-CDC45L/minor regulatory promoter was markedly enhanced when P-CDC45L/major and its regulatory promoter were deleted. The deletion analyses revealed the basal activities of the three core promoters, which were enhanced by approximately twofold by the respective regulatory promoters, on the transfected DNA templates.