‘While such ‘small-animal’ systems offer invaluable insights into fundamental biological questions, it is often misleading and perilous to unquestionably equate the higher order motor, sensory and cognitive processes that characterize human disease with that gleaned from a mouse or rat’ Enthusiasm for therapies based on the transplantation of exogenous cells or the transfer of genes by viral vectors has burgeoned over the past 30 years, accompanied by a predictable exhortation to launch clinical trials as soon as possible. Most data regarding safety, efficacy and mechanisms of these therapies have been derived from studies in rodents alone. While such ‘small-animal’ systems offer invaluable insights into fundamental biological questions, it is often misleading and perilous to unquestionably equate the higher order motor, sensory and cognitive processes that characterize human disease with that gleaned from a mouse or rat. Indeed, the literature is littered with clinical trials that failed and, in some cases, led to unforeseen adverse outcomes because the field leap-frogged over the requisite large-animal model. Large animals often provide an essential bridge between insights into fundamental biology and pathophysiology gleaned from simple systems and the realities of treating a human disease. Often, this is especially true for neurological disorders where not only differences in size and scale pertain, but also in neuroanatomical connections and organization, cognitive capacities, signaling pathways, genetic redundancy or the disease etiology. While the gene therapy field has increased their use of nonhuman primates prior to the application of viral vectors in clinical trials, the cellular therapy field – represented most conspicuously of late by the stem cell field – has only recently begun to properly address this requirement. Monkeys and the minipig may prove to be excellent preclinical models owing to their similar comparative anatomy, pharmacokinetics and physiological and metabolic