Background: - Lower respiratory tract infections are a leading cause of mortality worldwide,rncausing 1.6 million deaths annually in adults. Excluding tuberculosis they are the third mostrncommon cause of death worldwide and the most common cause of death in low-incomerncountries. Community acquired pneumonia is responsible for a large proportion of these deaths.rnGlobally, it is the leading cause of death from an infectious disease and the sixth leading cause ofrndeath overall. Studies in different settings of the world, attest to the fact that community acquiredrnpneumonia has a substantial clinical and economic burden. Despite its high morbidity andrnmortality globally and specifically in Ethiopia, community acquired pneumonia is not adequatelyrnresearched.rnObjective:-The aim of this study was to assess the epidemiology of community acquiredrnpneumonia among hospital treated adults in Tigray, Ethiopia.rnMethods:-The study was conducted in Tigray Region, north Ethiopia. A retrospective patientrnrecord review and case control study designs were used. The source population for the caserncontrol study design were both men and women aged 18 years and above who have beenrnattending their treatment in all zonal hospitals and Ayder Tertiary Hospital. Charts of all types ofrnpneumonia patients treated from July, 2013 to July, 2015 in all zonal hospitals of Tigray andrnAyder Tertiary Hospital were the source population for the retrospective record review. In thisrnstudy cases were patients of community acquired pneumonia who had been on treatment andrnfulfilled the definition for community acquired pneumonia, while controls were clients whorncame for some other purposes to the hospitals but without community acquired pneumonia. Tornassess the magnitude of community acquired pneumonia all medical records from the selectedrnhospitals of the period 2013 to 2015 were retrieved and the cost estimation was made from thernrecords of the period 2014 to 2015.The sample size for the case control study was calculatedrnusing two proportion formula with a case to control ration of 1 to 2.To collect the data semistructuredrninterviewer-administrated questionnaire and check list were adapted from differentrnliteratures .Once the data were collected, it was entered into Epi info 2002 and exported to SPSSrnVersion 20 statistical program for analysis. Ethical clearance was obtained from InstitutionalrnReview Board of the Addis Ababa University College of Health Sciences. Letter of agreementrnXIVrnwas secured from the Regional Health Bureau. Individual written informed consent was solicitedrnfrom the respondents at the time of data collection and examination.rnFinally measures of central tendency & proportion were calculated. The association between thernexposure and outcome variables were also determined using bivariate and multivariable analysis.rnData for cost was analyzed using descriptive statistics, numerical summary measures, and simplernlinear regression analysis. The method of cost estimation employed, included a bottom-uprnapproach in order to estimate direct patient side medical cost, whereas the indirect cost wasrncalculated using a human capital approach.rnResults: During the study period, there were 36,005 patients of all types of pneumonia withrn5877 cases of community acquired pneumonia, making the magnitude of community acquiredrnpneumonia to be 16%, with proportions for males (16%) and females (17%). The proportion ofrnadmitted patients due to community acquired pneumonia was 9.8%, with a mean admissionrnlength of 6 (+5.59) days.rnHistory of contact with pets, working in dusty environment, history of pulmonary tuberculosis,rnhistory of pneumonia, having contact with people who had respiratory infection, history ofrnrespiratory infection, history of tonsillectomy, history of upper airway problem, age andrneducational status had significant association with community acquired pneumonia in thernbivariate logistic regression analysis, while working in dusty environment [OR (95%rnCI);2(1.1,4.1)], history of respiratory infection [OR (95% CI); 2.3(1.5,5.7) ], contact with peoplernwho had respiratory infection [OR (95% CI);2.5(1.2,5.3)] and previous history of pneumoniarnconfirmed by radiograph [OR (95% CI); 39(19.4,78,6)] were significantly associated in thernmultivariate analysis.rnThe total amount of money incurred over the study year was 319,056.52 Ethiopian Birrrn($15,193.2). The direct medical expenditure was 242889.60 Eth.B ($11,566.20) and the cost ofrnlost working days by the patients due to community acquired pneumonia was 76166.92rnEthiopian Birr ($3627). From the cost of direct medical expense, 47.6 % was used forrnmedication, 18% for imaging (X-ray), 15% for laboratory, 16% for bed and 3% for registration.rnXVrnConclusion: The study revealed that the magnitude of community acquired pneumonia in thernstudy area was 16% and most prevalent among younger population. Working in dustyrnenvironment, having history of pneumonia, history of respiratory infection and having contactrnwith people who had respiratory infections are the risk factors of community acquiredrnpneumonia confirmed in this study.rnThe cost of illness among adult patients of community acquired pneumonia in the study area wasrnsubstantially high. Of the total cost incurred, 76 % was due to direct medical expense and 24 %rnfor the lost working days.rnHence, appropriate prevention strategies should be designed and implemented so that thernmagnitude of community acquired pneumonia would be minimized and terminally the treatmentrncost incur by the community acquired pneumonia will be reduced. Besides, Treatment guidelinernhas to be developed and proper management should be offered to prevent the re-occurrences ofrnprevious pneumonia and other respiratory infections as a result the development of communityrnacquired pneumonia would be minimized. Moreover, safety measures like personal protectivernequipments should be used when there is contact with patients having respiratory tract infections.rnMore so, further prospective studies should be conducted to estimate the magnitude andrncomprehensive costs of community acquired pneumonia. Larger studies are also needed to assessrnthe effect of some risk factors in the general population.