INTRODUCTION: Pseudomonas aeruginosa (P.aeruginosa) is a ubiquitous Organism that is often found in environment. It is a Gram-negative Bacillus, motile, straight (or) slightly curved measuring 0.5 – 8 Micrometer by 1.5 to 3.0 micrometer, non-spore forming, and Noncapsulated & obligate aerobes. Pseudomonas putida can appear Elongated. Organism from old culture may appear pleomorphic Gram Negative. Mucoid strains are seen as long filaments surrounded by Darker pink staining material (Alginate). Gram negative bacilli that are Showing intra cellular presence in polymorphonuclear leucocytes are Clinically important. Flagellar staining reveals single polar flagella. It Grows at wide temperature range between 6-42oc . Most pseudomonas species can reside in a wide variety of Environmental niches. Since their preferred temperature requirements Are between 4 and 36oc, Pseudomonas are found in processed foods, in Hands of health professional and they colonise animals and human. They Can spread among individuals. Ear infection and an irritating folliculitis may be acquired from Swimming pools, hot tubs. Community associated P. Aeruginosa Infections may occur as consequent to exposure to the organism in hot Tubs, whirlpools, and swimming pools. Keratitis due to P.aerugionsa May occur in individuals who store contact lenses in tap water and or Contaminated contact lens solutions. Intra venous drug users may Develop endocarditis and osteomyelitis as a result of injection of Contaminated injectables. P. Aeruginosa is also of nosocomial Significance The organism has been isolated from a variety of solutions Including soaps, ointments, irrigation and dialysis fluids, eye drops and Disinfectants as well as from fomites such as shower heads, respiratory Therapy unit, sinks, baths etc. Populations at risk for significant Morbidity and mortality include intubated patients in intensive care, Patients on chronic ambulatory peritoneal dialysis, and burns patients. Pseudomonas Species are associated with a number of Infections. They produce infections of wound and burns giving rise to Blue green pus. P. Aeruginosa can cause meningitis usually following Trauma (or) surgery. Corneal infections result from contaminated contact Lenses (or) injury, contaminated eye drops, and ointments. Pseudomonas Causes endocarditis through valve replacement. People who spend long periods for swimming are at risk for External ear infections (Swimmer’s ear). Malignant external otitis is a Virulent form of disease seen primarily in diabetes and elderly patients. P. Aeruginosa is the leading cause of chronic otitis media. Folliculltis is a common infection caused by Pseudomonas Species resulting from immersion in contaminated water (e.g. Hot tubs, Whirlpools, and swimming pools). Thermal burns of skin inhibit an Essential component of body defence against infection; the physical Barrier of intact skin .The resulting damaged tissue is a rich culture Medium and is a great risk for colonization and infection by Pseudomonas. Such infections have been the leading cause of morbidity And mortality. Infection of burn wound with Gram negative bacteria Typically occur one week after injury .The moist surface of the burnt Skin and lack of neutrophilic response to tissue invasion predispose Patients to such infections. Infections of the urinary tract are seen Primarily in patients with long-term indwelling catheter. The lungs of Children with cystic fibrosis are particularly susceptible to P. Aeruginosa. Use of ventilator which may introduce the organism to lower airways Produces lung abscess and pneumonia .The mortality rate is 70%. Epidemiological investigations of P. Aeruginosa infection have different Typing methods as follows 1 Biotyping 2. Antiobiotic Sensitivity Typing 3. Serotyping 4. Bacteriophage typing 5. Bacteriocin Typing 6. Modified Diene’s mutual Inhibition Test 7. Random Amplified Polymorphic DNA Study The Bacteriophage and Bacteriocin typing are outdated because Cross-reactions are more common. The Diene’s mutual inhibition test has been used as an Epidemiological tool to characterize Pseudomonas aeruginosa like Proteus mirabilis. The test was simple to perform and cheap and may Have utility in initial screening of P.aeruginosa isolates in suspected Common source epidemic. Genomic finger printing methods are now regarded as the most Accurate methods for the typing of microorganisms for epidemiological Purposes. These methods include pulse field gel electrophoresis, Ribotyping, and Polymerase chain reaction based finger printing (RAPD – PCR). In the present study, P.aeruginosa was isolated from heterogenous Clinical samples from patients attending Govt Rajaji Hospital, Madurai And were subjected to various tests to identify strain similarity. Further They were screened for similar homology using phenotypic test, Diene’s Mutual Inhibition test, and genotypic test RAPD – PCR.