Why might macrophages be of interest to neurobiologists? Recent evidence shows that macrophages play a role in tissue homeostasis as well as in defence and repair of tissues. We will review here the possible functions of resident and recruited macrophages in the developing and adult nervous system and examine what contribution these cells might make to repair mechanisms in the central and peripheral nervous systems. There is increasing evidence that macrophages form an important component of the non-neuronal cell population in the nervous system and the tools are becoming available that allow us to study these cells in situ.