We investigated the expression of sulfotransferases (STs) in the human colon carcinoma cell line, Caco-2, which is widely used as a human intestine model for orally administered drugs. By reverse transcription-polymerase chain reaction (RT-PCR), we could detect mRNA expressions of phenol STs (P-ST), hydroxysteroid ST (HS-ST) and estrogen ST (E-ST). Treatment with 1, 25-dihydroxyvitamine D₃, which induces CYP3A4 expression in Caco-2 cells, did not affect the ST expression of the cells. We detected significant P-ST activity toward 2-naphthol and dopamine in the cell extract. We also observed detectable HS-ST activity toward dehydroepiandrosterone (DHEA), but no E-ST activity toward β-estradiol was observed in the extract. Analyses by RT-PCR and separation of P-ST activities on ion-exchange column chromatography showed that the thermolabile monoamine phenol sulfotransferase (M-PST) is dominant in Caco-2 cells.