The efficacy of Generally Recognized as Safe (GRAS) acids (citric, formic, lactic, malic, phosphoric and propionic acids) was evaluated as possible alternatives to synthetic fungicides for the control of the economically important phytopathogenic fungi including Fusarium culmorum, F. nivale, F. solani, Macrophomina phaseolina, Rhizoctonia solani, Sclerotinia sclerotiorum and Uromyces appendiculatus. The concentration of acids that caused a 50% reduction (ED₅₀), the minimum inhibition concentration (MIC), and the minimum fungicidal concentration (MFC) values for mycelial growth, spore germination and germ tube elongation indicated that formic acid, propionic acid and phosphoric acid were generally more toxic to the tested fungi than the other acids. Therefore, formic and propionic acid were selected for further testing in soil. Formic acid and propionic acid completely inhibited the mycelial growth of S. sclerotiorum at 0.2%. These acids also completely inhibited the mycelial growth of both F. culmorum and R. solani at 0.6% in soil tests. Selected concentrations of acids were tested for efficacy against U. appendiculatus on bean plants in pots under controlled conditions. In these tests, control efficacy against U. appendiculatus of all acids ranged from 0 to 85.7%, with citric acid being the most effective treatment. The results of this study showed that the acids tested could become natural alternatives to synthetic fungicides for control of phytopathogenic fungi.