Background: Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic multidrug resistant (MDR) organism with high morbidity and mortality rate among hospitalized and immunocompromised patients. This is attributed to its natural resistance in addition to biofilm forming capacity. We aimed to detect the prevalence of biofilm between P. aeruginosa isolates and its relation to MDR. Methods: 191 P. aeruginosa isolates were collected from different clinical specimens after taking a written consent from the patients. The isolates were identified by standard microbiological methods. The disc diffusion was used to test the sensitivity of isolates to various antibiotics. Detection of biofilm phenotypically and genotypically was done. Results: Antibiotic susceptibility pattern of P. aeruginosa clinical isolates to different antibiotics showed that (56.5%), (52.9%), (47.6%), (47.1%), (47.1%), (46.6%), (44.0%), (43.5%), (40.8%) of P. aeruginosa isolates were resistant to CN, AK, AMC, ETP, IPM, PTZ, CAZ, CIP and CTX respectively. 69.1% of isolates were MDR. 84.3% were biofilm -producers by phenotypic method. The percent of genes encoding biofilm among 191 P. aeruginosa strains were 62.3%. 46.6% of the isolates presented all three genes “algD +, pslD +, pelF +”, 12.6% were “algD+, pslD +” genes, 3.1% were “pslD+” gene while 37.7% did not present any gene “algD−, pslD−, pelF–. Conclusion: Biofilm forming P. aeruginosa showed high MDR level and biofilm production is associated with presence of algD /pslD /pelF genes. البحث الثاني (بحث مشترك لم يسبق تقييمه)