An alicyclic amine N-sulfotransferase sulfonating 4-phenyl-1,2,3,6-tetrahydropyridine (PTHP) was purified from female rat liver cytosol and showed a homogenous band with a molecular weight of 30500 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme, designated NST-1, catalyzed sulfonation not only of the alicyclic amine but also dehydroepiandrosterone, a typical substrate of hydroxysteroid sulfotransferase (STs), but had little sulfonating activity towards 2-naphthol, a typical substrate of aryl STs. The N-terminal amino acid sequence for the first 24 residues had a high homology with those of rat liver hydroxysteroid STs. Therefore, it is suggested that NST-1 is classified as a member of the hydroxysteroid ST. Immunoblot analysis of male and female rat liver cytosol, carried out by using rabbit antisera raised against NST-1, indicated that the female cytosol contained a higher level of the enzyme than that of male. The marked sex difference in the expression level of NST-1 was in good accordance with the previous demonstration that female rat liver cytosol catalyzed sulfonation of PTHP to a greater extent than that of male.