The hydroformylation of hexene-1 is carried out in the biphasic system with RhCl(CO)(TPPTS)(2) (TPPTS = P(C6H4-m-SO3 Na)(3)), TPPTS and CTAB (cetyltrimethylammonium bromide). The rhodium catalyst concentration in interface has a drastic effect on reaction rate, and additional salts make reaction rate decrease obviously because they influence the distribution of catalyst in the biphasic system. Inorganic salts also have influence on the turnover frequency in the order: TOF(M3+) < TOF(M2+) < TOF(M+) (Mn+ is a metal cation with a charge of +n). However, additional inorganic salts do not change the regioselectivity obviously in this hydroformylation. (C) 2002 Elsevier Science B.V. All rights reserved.