Objectives: We performed a series of quantitative analysis of mRNA using reverse transcription(RT) PCR which is not only more sensitive than Northern blot but also does not require any radioisotope. For this purpose, standard RNA was designed and synthesized as the standard for quantitative RT-PCR. Using this standard RNA, we established the method of cytokine mRNA quantitation. We also tested whether imaging densitometry could replace the isotope use or not while in quantitation. According to this method, first, we studied cytokine gene profiles on human colonic epithelia cells, second, analyzed quantitatively those on the cells infected by the invasive enteric bacteria. Finally, we investigated the IL-8 mRNA expression of colonic mucosa in a patient with ulcerative colitis and a normal subject. Methods: The plasmid pHCQ encoding the synthetic RNA has the 5' and 3' priming sites for IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, TNF α, TGFβl, IFN-γ, β-actin, TCRα, TCRδ, CD4, and CD8, and the pGMC has those for MCAF and GM-CSF. Their arragement was designed to yield PCR products that differ in size by about 100 bp from those of the target RNA. After their sense and antisense primers were linked serially by oligo-nucleotide overlap extension and PCR amplification, each primer cassettes and poly(A) taill were subcloned into the plasmid, pGEM 3Zf(-), in order. And complementary standard RNAs were obtained by in vitro transcription. Using these standard RNA encoded from pHCQ and pGMC, we carried out quantitative RT-PCR for target RNAs extracted from cultured cells or tissue. Target RNAs were extracted by method using guanidinium thiocyanate-phenol-chloroform. Resu1ts: The size differences of PCR products from the standard RNA and the extracted target RNA were matched as designed. And the results obtained from either 32P-labelled PCR primer or imaging densitometry were also same. When the cultured colonic epithelial cells were infected by the invasive bacteria or stimulated by TNFα, proinflammatory cytokines, such as IL-8, TNFα, and IL-1β, were upregulated. And IL-8 mRNA was upregulated at the mucosa in a patient with ulcerative colitis comparing to that in a normal subject, Conclusion: These results suggest that synthetic standard RNAs encoded from pHCQ and pGMC are able to be used in quantitation of cytokine mRNA from cultured cells or biopsied tissue. In addition, human colonic epithelial cells may play a role in the host immune response by expressing mRNA for an array of cytokine which are already known to be important in the inflammatory reaction. In the near future, quantitative RT-PCR will be used widely in the studies of expression of specific human genes.