Bioassay-directed fractionation of Desmodium canum resulted in the isolation and characterization of three antimicrobial isoflavonones. These compounds, namely, desmodianones A, B and C, were assigned the structures 5,7,2'-trihydroxy-6,6"-dimethyl-6"-(4-methylpent-3- enyl)pyrano(2",3";4',5')isoflavanone, 5,2',4'-trihydroxy-7-methoxy-6-methyl-8-(3-methylbut-2-enyl)-is oflavanone, and 5,7,2',4'-tetrahydroxy-6-methyl-5'-(3,7-dimethylocta-2,6-dienyl )-isoflavanone, respectively.