The composition of hydrodistilled oils of the flower-heads and leaves of Cosmos bipinnatus was investigated by capillary gas chromatography coupled with mass spectrometry. Based on interpreting and comparing the resultant spectra with the available reported data, sixteen components were identified in the flower heads amounting to 91.58% and six in the leaves amounting to 98.28%. Hydrocarbons were found predominant in both oils and alcohols are present in variable concentrations, but the oxides were found in the flower-heads oil only. Both oils showed pronounced antimicrobial activity against certain micro organisms.