Sampling of study sites was based on availability of services in Hanoi and their level and function in the health care system. All hospitals in Hanoi that provide ARV, PMTCT and opportunistic infections (OI) treatment were selected, including all health facilities providing HIV testing. Additionally, all health facilities in one high-prevalence and well-resourced district were selected. In that district, interviews were carried out at all levels of the health system involved in PMTCT: district health centre, district maternity ward, district committee for family planning and mother and child health, and preventive medicine centres, including HIV testing sites. The research team also visited commune health stations in the district. Details are presented in Table 1 .