Background The number of people living with HIV worldwide continued to grow in 2012,rnreaching an estimated 34million .Sub-Saharan Africa remains the region most heavily affectedrnby HIV, In Ethiopia, the ART program started with a fee-based in 2003 then decentralized andrnfree ART program in the Country was lunched since 2005. Non-adherence to the proposedrnantiretroviral regimen is considered to be one of the greatest dangers to the response to treatment.rnObjective The main objective of this study is to determine the antiretroviral treatment adherencernand its associated factors among patients living with HIV/AIDS on combination antiretroviralrntherapy.rnMethodology: This is an institutional based cross sectional study. The study was conducted inrnAkaki kality sub city (Addis Ababa)from May to July. The study participants were selected byrnusing systemic random sampling technique. Data was collected in three health center that isrngiving ART service. Of Total of 2698 client 633 client whom currently on ART follow up wasrnsample study. Data was coded and entered in to Epi-info version 3.5.1and exported to SPSSrnversion 20 for analysis. Descriptive statistics was used to generate proportion and odd ratio andrnconfidence interval were calculated to assess the strength of associations of factors withrnadherence. logistic regression analysis was used to adjust or control the effect of different factor.rnResults: 88% percent of patients were adherent by self report in the month before thernassessment.12% percent of patients were non adherent by self report The major reasons reportedrnfor non-adherence were, Twenty one percent of patients asserted that they missed their doses duernto being away from home or having simply forgotten; while19.7% listed run out of medication asrnthe primary reason for treatment non-adherence. Other barriers to treatment included: being sickrn(15.8%),being busy (11.8%),went holly water (9.2%), being depressed (7.9%),self problem inrntaking medication(6.6%),being sleep (5.3%),work load(3.9%), confusion about dosagerndirection(3.9%) , fear of disclosure(2.6%), too many pills(1.3%),toxicity of the drug(1.3%),rntaking a drug remind me of my HIV(1.3%),people told the medicine is not good(1.3%).rnAssociated factors of adherence in the multivariate analysis controlling for independent variablernwere: not being depressed, education, having social support and being closer to home fromrninstitution during follow up.rnConclusions The adherence rates found in this study are comparable to those of other studies inrndeveloping countries but these rates are still low for good clinical outcomes. Since adherence is arndynamic process and patientâ€™s behavior can change over time, there is also a need to have arnfollow up design, which would yield a more valid average measure of adherence as well as itsrndeterminants than a cross-sectional self-reported adherence assessment. Programs and clinicalrnefforts to improve medication taking in the study setups should strive to manage depression withrna multidisciplinary approach, Educational programme should be developed focusing on thernpeople living with HIV-Aids.