Project Report (Thesis) to be Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science in Health Monitoring and Evaluation (Msc. HME) of Mzumbe University 2015The evaluation was looking into effect of engaging the lay workers in reduction of lost follow up among patients with advanced HIV/AIDS starting ARV’s. Specifically the evaluation was assessing the effect of intervention that reduce lost to follow up among patients with advanced HIV/AIDS starting ARVS and examine the factors that contributes to lost follow The assessment was retrospective cohort design conducted in three hospitals with HIV/AIDS care and treatment clinics in Dar es Salaam. Data of patients who were enrolled into project through study sites i.e Mbagala, Buguruni and Tandale for the period of February 2012 to September 2014 and followed up by lay workers for at least four visits was extracted from project database. The data was cleaned and analyzed by using statistical software Stata version 13. Descriptive and analytical Ztest was performed to compare lost to follow up of those clients followed up by the study team and the government CTC follow up A total of 435 patients information extracted from the database, 97 (22.3%) were from Buguruni, 141(32.4%) from Tandale and 197(45.3%) from Mbagala hospital. Out of 435 clients 383 (88.0%) were visited at least once and 52(12.0%) clients were reported of being lost to follow up, 11(11.3%) from Buguruni, 18(12.8%) from Tandale and 23(11.68%) from Mbagala. And the factors that contributed to it were clients education level of which those who did not attended school had higher chance (13/68) of being lost to follow up as compared to those with Secondary/University and this was statistical significant OR (4.1; 95%CI:1.1-15.2).Other reasons where:10(24.4%) client change of physical address and phone number, 4(9.8%) clients provided wrong map cue and 14(34.2%) they just move away to another area outside the study catchment area for business or medication Conclusion and Recommendations: Engaging the lay workers in fighting for lost follow up of HIV/AIDS starting ARVS especially in low and middle income countries like Tanzania which facing the problem of poor health staffs had shown a viii significant effect. Though issues of clients move away for business and others the like change physical address and phone number and wrong mapque location have been observed as the challenges during the follow up.