FIELD: organic chemistry. SUBSTANCE: carboxylic acids or appropriate esters thereof are prepared by interaction of at least one saturated alcohol C1-C10 with carbon monoxide. The process is carried out in the presence of iridium catalyst, halogen-containing promoter, water and solvent. Concentration of promoter, ester of acid, alcohol and water is maintained during reaction at level not more 10%, within 2-4 % and at level not more 10 % respectively. Carboxylic acid is also used as solvent. Catalytic system on the base of iridium carbonyl or iridium oxides prepared by their contact with hydrogen iodide acid and/or with precursor of acid is preferred. The process takes place in the medium of inert gas or in air. Molar ratio of hydrogen iodide acid and iridium is 1-100. EFFECT: improved efficiency of catalytic system. 10 cl, 3 tbl
