Biological studies on thirteen ethanolic plant extracts (Rosmarinus officinalis ,Ocimum basilicum , Moringa oleifera, Zingiber officinale, Curcuma longa, Nigella sativa ,Cinnamomum verum ,Salvia officinalis, Lepidium sativum, Foeniculum vulgare, Anethum graveolens, Ficus benghalensis and Cinnamomum camphora )revealed that four of them (Rosmarinus officinalis , Zingiber officinale, Cinnamomum verum and Cinnamomum camphora) were the best active against two  bacterial species ;  E. coli , S .aureus  and  one fungus species  C. albicans. Also, their synergistic effects against E. coli, S. aureus  and  C. albicans were studied .So, the phytochemical studies were completed on these four  plants . This study aimed to evaluate the chemical composition of the best active plant extracts. The chemical   major content of   Rosmarinus officinalis  was eucalyptol  (7.48%)   , Zingiber officinale was gingerol (12.73%) , Cinnamomum verum  was      (E)-  cinnamaldehyde (25.55  %  )  and Cinnamomum camphora was eugenol  ( 27 .35% ) . The minimum inhibitory concentration (MIC) values varied from 0.625 to 2.5 mg/ml, for the S. aureus (gram positive bacteria) affected by Rosmarinus officinali,  Zingiber officinale, Cinnamomum verum and Cinnamomum camphora. Respectively. C. albicans was the most effective microorganism by Cinnamomum verum and the least effective microorganism by Rosmarinus officinalis and Cinnamomum camphora. ethanolic extracts, as MIC ranged from 0.15 to 1.25 mg/ml.