Fresh samples of  Salvadora  persica   were collected  from Hudiadah  province  at 23/2/2011 . They include  stems ,roots, and  leaves  . The ethanolic and aqueous extracts were prepared as w/v . (2.5, 5, 10 )% for three plants parts .                                                                                             
      The microbial samples were collected from privet dentists clinics in Thamar  province by mouth swab and mouth  washing  methods . S. aureu s S. mutans, , and C. albicans  were isolated and a pure cultures were  prepared to each microbes for farther studies .The effect of different parts of plant showed high antimicrobial activity of root extract followed by stem and leaves extracts and the antimicrobial effecacy concern positively with  concentration. The ethanol extract  showed more antimicrobial activity than hot water extract.