In the Kisumu Breastfeeding Study (KiBS), prevention of mother-to-child HIV transmission study, highly active antiretroviral therapy (HAART) is provided from 34 weeks gestation, through delivery to six months postpartum. The study recommends that women practice exclusive breastfeeding for six months, then wean abruptly. We sought to explore factors such as, education, family support, cultural norms, and sources of information about perinatal HIV transmission, which may influence a mother's decision to comply or not comply with the study's recommendation to stop breastfeeding when HAART is discontinued. We used semi-structured interviews of a purposive sample of 18 mothers participating in the KiBS. By interviewing 10 mothers who stopped breastfeeding and eight mothers who continued, it was possible to examine how different factors may have affected the groups of participants. All participants stated that it was not traditional to stop breastfeeding at six months. Participants who stopped breastfeeding reported more family support, were more educated, and were more likely to disclose their HIV status. Participants who continued breastfeeding more often expressed concern about stigma. Participants learned about mother-to-child transmission from clinics, churches, community groups, and other HIV-positive mothers. This substudy suggests that family support, education, and cultural norms are important factors that may influence a mother's decision regarding breastfeeding cessation. Thus, counseling and family support may play integral roles in the promotion of early breastfeeding cessation.