Background: Mother to child transmission (MTCT) of HIV constitutes a major source of new pediatric infections in Cameroon. Objective: The aim of this implementation research was to assess outcomes and effectiveness of providing lifelong antiretroviral therapy (ART) for HIV-positive pregnant and breastfeeding women (Option B+). Methods: From October 2013 to July 2014, HIV-positive pregnant and breastfeeding women, not on antiretroviral (ARV) prophylaxis and ART, were recruited from 22 purposefully selected health facilities in the Northwest and Southwest regions for a prospective, observational cohort evaluation. Option B+ was offered to participants and outcome indicators were measured. Results: Out of 680 women eligible for this assessment, 669 (98%) were initiated on Option B+. Retention-in-care was 90% (95% CI, 87.85-92.61) and 79% (95% CI, 75.20-81.88), and loss to follow up (LTFU) was 7% (95% CI: 4.95-8.90) and 15% (95% CI: 12.06-17.56) at 6 and 12 months respectively. Maternal mortality at 12 months after ART initiation was 2% (13). As of March 2015, 538 HIV exposed infants