This Horizons report describes the evaluation of an intervention study in Kibera, an urban slum in Nairobi, to determine what effect three different community-based activities had on utilization of key prevention of mother-to-child transmission (PMTCT) services. The interventions included moving services closer to the population via mobile clinics, as well as increasing psychosocial support through the use of traditional birth attendants (TBAs) and peer counselors as PMTCT promoters.