The hexane, chloroform, methanol extracts of Cassia Siamea leaves on chromatography yielded nine compounds which were identified as Stigmasterol, Lupeol acetate,2-methoxy-4¢ -hydroxy-3¢ ,5¢-diprenylchalcone,Chrysin, Chrysophanol, Kaempferol, Quercetin, 2-methyl anthraquinone, 3,7,-dimethoxy-3¢ , 4¢-methylenedioxy flavone. These were characterized by chemical tests and spectral means (UV, IR, MS, 1H NMR). The three extracts and some isolated compounds were screened for antimicrobial studies. A moderate activity was observed on tested organisms.