The method is applicable to a product containing 35 % (m/m) to 60 % (m/m) of m-cresol, not more than 5 % (m/m) of phenol, and not more than 35 % (m/m) of o-cresol. The principle is based on dehydration of a quantity of the test sample. Formation of a complex between m-cresol and urea by addition of excess urea to a test portion of the dehydrated sample. Determination of the crystallizing point of the complex in a crystallizing point apparatus. Calculation of the content from the water content of the test sample and the crystallizing point of the complex. The relation between crystallizing point and m-cresol content of m-cresol/urea mixtures is given in a table. ISO 1897/9 replaces ISO Recommendation R 1911-1971.