Deficiency in immune cell number or activity is a cardinal feature of HIV. Second line antiretroviral therapy is geared towards improving immune cell activity and improving treatment outcomes. More people are now accessing free combination antiretroviral therapy through public health programmes in resource limited settings. There is currently no third line therapy for patients failing second line therapy in most of these programmes and data on effectiveness of second line antiretroviral therapy are limited. To adequately address and prepare for this scenario, critical assessments of the outcomes of second-line cART are needed. This is a retrospective cohort study of patients accessing second line cART at the APIN/ JUTH, Jos adult HIV clinic from 2004 to 2018, to determine the proportion of patients failing second line cART, to evaluate time to immunologic failure, time to lost to follow up and time to death using Kaplan Meier estimates. Immunological failure occurs when there is a fall of CD4 counts to pre-therapy baseline (or below) or 50% fall from the on-treatment peak value (if known) or persistent CD4 levels below 100 cells/mm 3 6 months after ART initiation. A total of 285 patients were included in the study, with a mean age of 45±9.5 years. Females where 194 (68.1%) All the patients were on boosted protease inhibitor, the predominant combination antiretroviral therapy for second line regimen was Lopinavir boosted with ritonavir in combination with Tenofovir, Lamivudine and Zidovudine (43.9%). The baseline CD4 count was 134 (IQR 54-272). The CD4 count increased to 339 (IQR213-498) at 72 weeks. In conclusion, Second line cART immunologic failure rates are low in our cohort and patient stay longer on cART before failure. Keywords: CD4 cells, Immunologic failure, Antiretroviral therapy DOI: 10.7176/JHMN/107-02 Publication date: April 30 th 2023