Carbonylation of formaldehyde with carbon monoxide over zeolite catalysts has been investigated. Compared with resins (Amberlyst-15 and Amberlyst-70), and phosphotungstic acid, the zeolite catalysts especially ZSM-5 showed very high selectivity to methyl glycolate. The selectivity of ZSM-5 was maintained to high temperature up to 200 A degrees C.