Background: Adult mortality rate is the probability of dying between the ages of 15 and 60. Levels andrntrends in overall adult mortality have important implications for health and social program. Globally,rnadult mortality rate has been declining in the period of 1990 and 2012 though countries in sub-SaharanrnAfrica showed increase in adult mortality. Despite this increase, adult mortality remains a neglectedrnpublic health issue in Sub-Saharan Africa. A lack of empirical data about the levels of mortalityrnexperienced by adults in this region has fueled this neglect. Thus, analyzing data from continuousrnsurveillance system can be a corner stone to the development of reliable data on trends and risk factors forrnadult mortality.rnObjective: To assess trends and identify determinants of adult mortality in Butajira, South CentralrnEthiopiarnMethods: Both quantitative and qualitative studies were conducted. The Butajira database running fromrn1987-2008 was extracted and analysed using STATA 12. The trend of adult mortality was computedrnusing event history analysis and Poisson regression analysis was used to calculate IRR with 95% CI. Forrnthe qualitative part, data were collected from community leaders, staffs of health and agriculture officesrnand the BRHP to strengthen the result from quantitative part of the study. Open code 3.6 Software wasrnused to code and categorize qualitative data and themathic analysis was employed.rnResult: There was a significant decline in adult mortality, with some ups and downs in levels during thernsurvey years.This was due to ill behaviours, social upheavals, food insecurity, health service relatedrnproblems and occurrence of epidemics at different times.The incidence of adult mortality was found to bern6.57(6.33, 6.82) adult deaths per 1000 person years. There were higher incidences of female adultrnmortality with a level of (95%CI) 7.14 (6.78, 7.52). The incidence of adult mortality significantlyrnincreased with age. Married, divorced and widowed adults had higher incidence of death with adjustedrnIRR (95% CI) 1.71(1.52, 1.91), 2.93(2.11, 4.06) and 4.90(4.25, 5.66) respectively compared to thernsingles. Adults who were illiterate, resided in rural areas, confessed in Muslim religion and did not havernwindow for their houses had significantly higher incidence of death with IRR (95% CI) 1.12(1.02, 1.23),rn1.27(1.02, 1.57), 1.15(1.05, 1.26) and 1.20(1.08, 1.34) respectively.rnConclusion: The incidence of adult mortality showed a declining trend mainly due to social andrnbehavioral problems. Age, residence, religion, marital status, availability of windows were significantlyrnassociated with incidence of adult mortality.Awareness creation with prevention of different diseases andrnensuring food security are recommended to health and agricultural sectors respectively.Furthermorernstakeholders are advised to work on decreasing the work burden of females and their empowerment