A master's thesis at the faculty of science collage at the University of Basrah (The phenotypic and genotypic investigation of resistant pattern and biofilm formation of Staphylococcus aureus isolated from healthy and tonsillitis patients), and showed the researcher's thesis (Maysoon Khaleel Ibrahim). Thesis aims to This study aims to build up a data base for Staphylococcus aureus bacteria by Isolate and identify methicillin-resistant staphylococcus aureus, Investigate the presence and the role of Intracellular adhesion molecules genes ica in biofilm producer S aureus. Isolated about 300 samples from healthy people and tonsillitis patients in Basrah City, by using the biochemical test, and molecular technique. The study concluded that there is resistance to antibiotics in many healthy samples, especially oxacillin, vancomycin and cefoxitin. The presence of genes ica is necessary for the formation of biofilm, in addition to the approval of the D-shape test to discover the antimicrobial interaction that may occur between the Erythromycin and Clindamycin. The study recommended more studies of the adhesion genes of S. aureus bacteria and the role of ica operon in regulating the genes of these bacteria and diagnosis of more sensitive methods for phenotypic evaluation of biofilm production.