Continuous Quality Improvement (CQI) is a process where health teams systematically collect and regularly reflect on local data to inform decisions and modify local practices and so improve delivery of services. We implemented a cluster randomized trial to examine the effects of CQI interventions on Prevention of Mother-to-Child Transmission (PMTCT) services. Here, we report our experiences and challenges establishing CQI in 2 high HIV prevalence states in northern Nigeria. Facility-based teams were trained to implement CQI activities, including structured assessments, developing change packages, and participation in periodic collaborative learning sessions. Locally evolved solutions (change ideas) were tested and measured using process data and intermediate process indicators were agreed including overall time spent accessing services, client satisfaction, and quality of data. Health workers actively participated in clinic activities and in the collaborative learning sessions. During the study, the mean difference in time spent accessing services during clinic visits increased by 40 minutes (SD = 93.4) in the control arm and decreased by 44 minutes (SD = 73.7) in the intervention arm. No significant difference was recorded in the mean client satisfaction assessment score by study arm. The quality of data was assessed using a standardized tool scored out of 100; compared with baseline data, quality at the end of study had improved at intervention sites by 6 points (95% CI: 2.0 to 10.1). Health workers were receptive to CQI process. A compendium of "change ideas" compiled into a single change package can be used to improve health care delivery.< Réduire