Abstract: The growth response of two fungi, Cladosporium herbarum (Link.) Fr. and Trichothecium roseum (Bull.) Link., was studied on six carbon sources at three concentrations. Sucrose proved to be the best carbohydrate source for Cladosporium, but Trichothecium could not use this compound for growth. Glucose, mannose and fructose were utilized almost equally well by C. herbarum. Glucose was the best carbohydrate for T. roseum, and mannose and fructose were also growth-promoting. Galactose and arabinose proved to be very weak carbon sources for both fungi. It seems evident that the carbohydrate composition of the nutrient medium must have a great effect on the growth of these fungi.