Background  The effects of diabetes mellitus on human include long term dysfunction and failure of various organs. A number of oral diseases and disorders have been associated with diabetes mellitus. The susceptibility to periodontal disease often called the "sixth complication of diabetes mellitus" is the most common oral complication of diabetes. The oral cavity is comprised of many surfaces, each coated with a plethora of different bacteria, some of which have been implicated in oral diseases such as caries and periodontitis.  Objective  This study was conducted to determine the most common microorganisms inhabiting the oral cavity of diabetic individuals in comparison to non diabetics, to determine the relation of oral microflora to oral conditions in diabetes and determine the susceptibility of oral microflora to common antimicrobial agents.  Methods  A case control study on two hundred persons with type II diabetes mellitus and fifty control cases. Oral findings were documented based on physical examination, microbial identification was based on culture methods and various identification tests. Antimicrobial susceptibility was performed according to Kirby- Bauer method.  Results  The oral findings in persons with type II diabetes mellitus showed higher occurrence of gingivitis, periodontitis, dental pain, xerostomia, taste disturbance, palatal ulceration and oral candidiasis in comparison with person without diabetes. Microorganisms studied by culture-dependent methods showed more bacterial isolates in diabetic groups of many stains such as of Bacillus species, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophyticus, Streptococcus pneumoniae, Streptococcus pyogenes, Viridans streptococci, Branhamella catarrhalis, Escherichia coli, Stomatococcus, Veillonella and Candida albicans. The bacterial isolate susceptibility to antimicrobial agents showed wide resistance to several commonly used antimicrobial agents in dental practice and intermediate response was shown to be arising to some antimicrobial agents. Conclusion  Various oral and dental problems such as periodontitis and dental loss was observed in diabetics, also more microbial isolates were documented from diabetics with a notable shift to more virulent species. Most of the isolated organism were resistant to several commonly antimicrobial agents in use. Oral problems may reflect on the increasing oral population of certain bacterial species and this will further complicate their oral problems.