Aims and objectives: Acinetobacter, gram–negative non–motile bacilli 1^st isolated from soil responsible for nosocomial and opportunistic infection in hospital demonstrates multidrug resistance for last 2 decades due to irrelevant use of different broad spectrum antibiotics. This present study tried to demonstrate spectrum of antimicrobial sensitivity of acinetobacter to different antibiotics. Materials and methods: In this retrospective study sputum was isolated from the 1078 patients suffering from lower respiratory tract infection of K P C Medical College & Hospital, Jadavpur, and Kolkata and sent to bacteriology department for isolation of the organism followed by antimicrobial sensitivity. Results: Total number of acinetobacter spp. positive patients was 110 (10.20%). These bacteria was more than 90% sensitive to polymixin B and colistin, 56.36% positive to tigicycline and 37.27% to 39.09% to carbapenem, 23.63% to 26.36% to aminoglycosides. Rest of the antibiotics demonstrated high resistance. Conclusions: Due to increasing resistance of these bacteria to different broad–spectrum antibiotics, one should not use this antibiotic to start with. In that case we have no option other than to use polymixin B or colistin or tigicycline. So it may be a resolution that only after getting proper sensitivity report we can use proper antibiotics, only this can prevent the creeping of resistance to antibiotics.