The chemical compounds present in the essential oil of the different plant parts viz., rhizome, root, stem, leaves and flowers of Costus pictus D. Don were identified by GC MS method. The antimicrobial studies of these essential oils were carried out by disc diffusion method. Diosgenin, a steroidal saponin has been isolated for the first time from the roots of Costus pictus. The diosgenin content in the root of Costus pictus was quantified by HPLC method.