Background: Nosocomial infections (NIs) remain a significant cause of morbidity andrnmortality both in developed and developing countries. NIs is caused by the microorganismsrnthat are commonly found around the hospitals. In the hospital environment, medicalrnequipments carried by HCWs such as otoscopes and stethoscopes may serve as the reservoirrnfor microorganisms. rnObjectives: This study was undertaken to determine microbial colonization of otoscopesrnand stethoscopes used by HCWs at Tikur Anbessa Specialized Referral Hospitals, AddisrnAbaba, Ethiopia, between November 2011 and April 2012. rnMaterials and Methods: 130 stethoscopes and 6 otoscopes were sampled from differentrnhealth personnel of five wards. Cleaning trends of stethoscopes and otoscopes by HCWsrnwere assessed through the prepared questionnaire. Swab sample was taken by rubbing therndiaphragm and bells of stethoscopes as well as handles and tips of otoscopes with sterilerncotton tip applicator moistened in sterile saline. The swabbed sample was inoculatedrnimmediately on blood agar and Sabouraud dextrose agar for bacterial and fungal growthrnrespectively. Identification of bacteria were done using gram staining, colony morphology,rnbiochemical tests include catalase and coagulase tests (for gram positive bacteria), oxidaserntest and API 20E (for gram negative bacteria). Germ tube test, LPCB staining, gram stainingrnand thermo tolerant growth test were done for identification of fungal species. For bacterialrnisolates, antibiotic susceptibility test were done by disc diffusion method according to thernpreset criteria and the result were interpreted as susceptible, intermediate and resistance byrnmeasuring the growth inhibition zone. rnResults: From the total of 136 medical devices (6 otoscopes and 130 stethoscopes) sampled,rn82(60.3%) were colonized with different species of bacteria (n=99) and fungi (n=12). Fromrnthe total of bacterial colonization, gram positive bacteria accounted for 94(94.9%) where asrngram negative bacteria accounted for 5(5.1%) and fungi accounted for 12(10.8%). Amongrnthe bacteria isolates, CoNS were dominated and of fungi, Candida albicans were dominated.rnOf the 130 stethoscopes sampled, 70(53.8%) showed bacterial colonization and 9(6.9%)rnwere showed fungal colonization. Among different HCWs, 31(70.5%) of stethoscopes from resident medical doctors and also among the five wards, 25(71.4%) of stethoscopes fromrnICU were showed high rates of microbial colonization. Five (45.5%) and 74(62.2%) ofrnstethoscopes that cleaned and not cleaned between patients examination respectively werernshowed microbial colonization. And also 60 (57.1%) and 19(76.0%) of stethoscopes thatrncleaned with disinfectant and not cleaned with any disinfectants respectively were showedrnmicrobial colonization. rnS.aureus and CoNS isolates were showed low level of resistance (