The methoxycarbonylation of propylene oxide (PO) to methyl P-hydroxybutyrate (MHB) catalyzed by dicobaltoctacarbonyl ([Co-2(CO)(8)]) and 3-hydroxypyridine (3-OH-Py) in methanol system has been studied. The effects of different additives, the molar ratio of 3-OH-Py:Co2(CO)81 temperature, carbon monoxide (CO) pressure, reaction time on the conversion and selectivity have been investigated. The conversion of propylene oxide is 80.4%, and the yield of methyl P-hydroxybutyrate is 74.9% with selectivity 93.2% when the reaction is carried out for 16 h at 80 degrees C and 6.0 MPa of CO in methanol, with 0.125 nmol of Co-2(CO)(8), 0.25 mmol of 3-OH-Py. The mechanism of this catalytic reaction has also been proposed. (c) 2006 Elsevier B.V. All rights reserved.