The human gene encoding the transcription elongation factor SII (TFIIS) was isolated and characterized. The comparison of sequence between TFIIS gene and cDNA showed that TFIIS gene doesn``t carry any intron sequence. Based on Southern blot analysis and independent screening with 2 different genomic libraries, the gene appears to exist as a single copy in the haploid genome. Also, TFIIS protein expressed in E. coli from the cloned TFIIS gene stimulates RNA polymerase II transcription by 4-fold. The transcription initiation site was determined by S1 nuclease mapping. TFIIS promoter carries typical CCAAT box at-59 position existing in opposite orientation, and initiator sequence around the transcription initiation site. However, obvious TATA box couldn``t be found and potential Spl recognition sequences was found at 189 and 381 nucleotides upstream from the transcription initiation site. These structural features are similar to the promoters of many housekeeping genes, whose activity is required in all cells and is not subject to environmental control.