Libraries constructed from immunised non human primates (NHP; macaques here) are an appealing alternative to human libraries when immunization of Humans is difficult, as is so often the case. These phage-displayed libraries allow to obtain antibody fragments of very high affinities (nano- to picomolar), and diverse epitopes are targeted so that antibodies with the desired activity can be isolated. Due to their high similarity with their human counterparts, NHP antibodies might be readily humanized or germline-humanized, to ensure an excellent tolerance for medical use. Practical peculiarities of this convenient approach, as well as legal aspects, will be considered.