Breastfeeding mothers and their babies are important members of society in all countries. More than half of mothers will require medication whilst breastfeeding, but there are substantial gaps in understanding transfer of drug from mother to breastfed child. In many parts of the world where conditions such as HIV, TB, malaria, neglected tropical diseases and outbreaks of high-consequence pathogens are prevalent, breastfeeding is usually the only affordable, feasible, acceptable, sustainable and safe infant feeding option. It is therefore imperative that the development of new drugs includes evaluation of lactation pharmacology. This talk will include recent data on drugs used to treat some of these conditions in lactating mother-infant pairs, illustrate best practice in study design, and draw upon a decade of experience working in lactation pharmacology in Uganda. Furthermore, it will emphasise the key role of community engagement and involvement in all stages of study design, from establishment of research priorities through to dissemination of results.