It is well documented that social housing is fundamental to good welfare for non-human primates (NHPs). Despite this, many laboratory NHPs around the world continue to be singly housed, though usually with visual, auditory and olfactory contact with conspecifics. Most relevant legislative texts and professional guidelines stipulate that single housing should be used only when justified on strong scientific or animal health grounds. However, the interpretation of strong grounds by practitioners, regulators and ethics committees/IACUCs clearly differs between countries and research facilities. This is evident from the peer review of research proposals that the NC3Rs performs for the major UK research funding bodies. In the UK single housing is truly exceptional for NHPs; whereas overseas NHPs are often housed singly for reasons that would not be acceptable or necessary in the UK. The NC3Rs has been able to challenge these reasons and work with funded researchers and facilities to enable social housing. This short presentation will outline some of the factors that facilitate successful social housing, and invite some discussion of these with the audience.