Nafion-H was used as a solid acid catalyst for the Koch-type carbonylation of alcohols. The carbonylation of a variety of primary, secondary and tertiary alcohols in various solvents such as hexane, cyclohexane, dichloromethane and chlorobenzene produces the corresponding tertiary carboxylic acids in high yields. For example, the conversions of 2-methyl-2-propanol, 1-pentanol and 1-adamantanol to carboxylic acids are 62.5, 64.6 and 76.9%, respectively, at 433 K and 9 MPa CO. The optimum temperature for this reaction is between 433 and 443 K. A high CO pressure is advantageous for the carbonylation. Only small amounts of ethers were observed for the primary alcohols under CO pressure and without water removal, in contrast with the previous report that primary alcohols are converted to ethers over Nafion-H in quantitative yields when CO is absent and water is removed by azeotropic distillation. (C) 2002 Elsevier Science B.V. All rights reserved.