Introductioná¡ Adherence to ART among HIV positive pregnant & lactating mothers is arncentral component in PMTCT to reduce viral loads & achieve elimination of mother to childrntransmission of HIV. Option B+ PMTCT programme is a recently introduced approach torneliminate new HIV infection among children. This approach is based on treatment asrnprevention to mean starting lifelong ART for all HIV positive pregnant & lactating mothersrnwithout considering CD4 count or clinical stage of HIV/AIDS disease.rnObjectives: The aim of this study was to measure the level of adherence and identify factorsrnassociated with adherence to option B+ PMTCT programme among pregnant & lactating mothersrnin selected government health facilities of south wollo zone, Amhara region, north east EthiopiarnMethod: An institution based cross sectional quantitative study design was used. The study wasrnconducted in two hospitals & five health centers found in south Wollo zone, Amhara region. Thernsample size required for this study was 191 HIV+ pregnant & lactating mothers who were onrnPMTCT follow up. The study subjects were taken consecutively until the sample size was metrnfrom March 1 to April 14, 2016. Standard structured data collection instrument was used & itrnwas collected by using face to face interviewing. The data were entered in to EpiData 3.1 thenrnexported to statistical package for social science (SPSS) window version 21 for analysis. Enteredrndata were explored for errors & missing values then it was cleaned before analysis. Bivariate andrnmultivariate logistic regression analyses were employed to identify associated factors forrnadherence. P-value less than 0.05 with 95 % confidence interval was used to state the associationrnbetween independent predictors and the outcome variable.rnResult: A total of 190 HIV+ pregnant & lactating mothers were included in this study. Thernlevel of adherence on option B+ PMTCT drug was 87.9 %. Factors such as those who attendrnin Hospital(AOR 0.3,95% CI(0.11-0.82), rural residence (AOR 0.26, 95%CI (0.1-0.73) andrnthose who faced challenges in the same day diagnosis of HIV and initiating lifelong optionrnB+ treatment (AOR 0.08, 95%CI (0.02-0.37) were associated factors for adherencernConclusion & recommendation: mothers who attended for option B+ drugs in healthrncenters, those who lived in urban area and who had no any challenges in same day diagnosingrn& initiating option B+ drugs were significantly associated factors for better adherence tornoption B+drugs. Therefore, the ability to effectively handle these factors is crucial in thernsuccess of option B+ programme.rnKey words: adherence, Option B+, HIV+ pregnant & lactating mothers, north east Ethiopia