Selecting a pharmacologically relevant animal species for testing the safety and toxicity of novel monoclonal antibody (mAb) therapies to support clinical testing can be challenging. Frequently, the species of choice is the primate. With the increased number of mAbs in the pharmaceutical pipeline, this has significant implications for primate use, and so raises several important scientific, ethical and economic issues. Here, following a recent international workshop held to debate this topic, we discuss issues in the preclinical testing of mAbs, with a particular focus on species relevance and primate use, and provide suggestions for how these issues might be addressed.