Background: Although there is a significant improvement in maternal health service in recent years,rninequalities in the utilization of ANC service remain to be a challenge in Oromia region. In thisrnstudy, we aim to provide a comprehensive analysis to examine the trends in inequalities in thernutilization of ANC service and its associated factors among women aged 15-49 years in Oromiarnregion between 2000 -2016 EDHS.rnMethods: Women in the most recent birth data from regional representative surveys in Oromiarnregion in the four consecutive EDHS rounds was used. Trends in inequalities of ANC servicernutilization were measured using a combination of RD, RR, CIX, SII, and RII,and is subsequently rndecomposed into contributing factors. Multivariable logistic regression analyses using GLMrnapproach were carried out to identify the factors of ANC utilization. A p-value of < 0.05 and 95% CIrnwas reported as a measure of magnitude of significance. Data analysis was done using STATArnversion 14 and Microsoft ExcelÂ© 2016. rnResult: Over 16 year period, the percentage of women who revieved ANC1+ and ANC+4 visitsrnincreased significantly from 27.3%, 10.2% in 2000 to 51%, 22.2% in 2016 EDHS respectively.rnAlthough ANC services showed an upward trend from 2000-2016, there was very low utilization ofrnANC services influenced by socio-demographic and economic factors in the region. Trends in RDrnand RR of any ANC use were analyzed. The overall CIX for any ANC services utilization amongrnwomen significantly an increased trend from 0.79 in 2000 to 0.99 in 2016 EDHS. By contrasts, anrnestimate of CIX indicates declined significantly for wealth status from 0.279 in 2000 to 0.133 inrn2016, education level from 0.247 in 2000 to 0.134 in 2016, and disparity of urban-rual areasrndecresed from -0.204 in 2000 to -0.062 in 2016) respectively. The RR &RII of any ANC servicesrnutilization with socioeconomic status was significantly decreased while the RR of wealth status &SIIrnby educational level among women were slightly increased significantly between 2000-2016. Wealthrnstatus & women's education were the most significant contributors to inequality in ANC visits.rnInequalities in use of ANC favoured advantageous women over their counterparts. The findings ofrnthe present study shows that these disparities continue to persist in the region.rnConclusion: The findings show that utilization of any ANC services is very low. The findings of thernstudy show that there was inequality in any ANC service utilization in Oromia region. The socioeconomicrnrnfactors such as residence, level of education , and economic status were the determinantsrnof inequality. There is a need to increase the availability, accessibility and affordability of healthrnservices to all women, especially for the disadvantaged, uneducated and those who live in hard-tornreach rural areas in the study area. Finally, the regional government should scale up of strategies thatrnare pro-poor to increase ANC service provision in underserved areas are crucial.