Box-Behnken Antimicrobial Anti-tumor Thirteen different attached marine bacteria were isolated from the surface of algae, rocksin biofilm forming device in Red Sea. They were screened for their potentiality in the exopolysaccharides (EPS) production. The most potent marine isolate 2D was identified by 16S rDNA analysis as Halomonas saccharevitans AB2 with 99% similarity. Optimum culture conditions which ease the synthesis of EPSsfrom Halomonas saccharevitans AB2 were evaluated. It grew well at 25˚C, pH 9 and on potato sea water extract with concentration 100%, lactose and malt extract as the best carbon and nitrogen sources. Application of Plackett-Burman experimental design achieved the maximum yield of EPSs (138 gl-1) with 1.4 fold increase when compared to growth under the basal conditions. The maximum yield of EPSs (153gl-1) with 1.6 fold increase was obtained upon applying Box-Behnken design. The EPSs showed antimicrobial activity by inhibition of different pathogenic bacteria and fungi with the maximum absolute unit (AU= 14.1 and 25.1) against Vibrio fluvialis and Aspergillus niger ATCC 16404, respectively. Moreover, these EPSs exhibited activities as antitumor agent against 8 cell lines with maximum inhibition (87%) at 50 μg with IC50 =20.3 μgml-1 against human lung carcinoma (A-549). Potential antimicrobial and antitumor activities property of EPSs produced by H. saccharevitans AB2 may lead to the development of novel medical drugs.