There is substantial evidence that early childhood development (ECD) programming can improve child health and development outcomes. An important component of ECD programming is supporting positive parenting and early stimulation practices. While many parents could benefit from such programming, mothers that are HIV-infected may particularly benefit given the higher risks of poorer child development among HIV-exposed children. Catholic Relief Services (CRS) in Cameroon is implementing the Key Interventions to Develop Systems and Services (KIDSS) ECD program for HIV-exposed children. The program will include home-, facility-, and community-based components. This impact evaluation will ascertain to what extent the KIDSS home-based component of the ECD model affects attainment of age-appropriate developmental milestones (measured by the Ages and Stages Questionnaire 3 (ASQ-3)) in HIV-exposed children in Cameroon. The study design is a cluster-randomized controlled trial with a cohort of 200 mother/child dyads across 10 study clinics. HIV mothers will be recruited during pregnancy and their children will be followed up until 18 months of age. The intervention group will receive regular home-based ECD services focused on positive parenting and early stimulation as well as exposure to facility- and community-based ECD programming. The control group will only have exposure to the facility- and community-based ECD programming. Randomization occurs at the clinic (cluster) level.