We have previously demonstrated that delivery of a recombinant adeno-associated virus (rAAV) encoding human alpha-iduronidase (hIDUA) in the putamen and centrum semiovale was feasible and beneficial in a dog model of Hurler's syndrome. In the present study, we investigated the safety and vector diffusion profile of three rAAV serotypes (rAAV2/1, rAAV2/2, and rAAV2/5), encoding hIDUA in the central and peripheral nervous systems of nonhuman primates. Six macaques received the same vector dose injected into the right putamen and the homolateral internal capsule. Neurological examinations were done regularly and showed no detectable clinical consequence of the intracerebral injections. Because transgene IDUA was indistinguishable from endogenous enzymatic activity, we looked for vector diffusion by performing quantitative polymerase chain reaction on serial sections from the brain and spinal cord. We found that global diffusion throughout the brain was not significantly different between the three serotypes. However, rAAV2/1 and rAAV2/5 resulted in higher vector copy numbers per cell than did rAAV2/2, respectively, in the brain and the distal neuronal structures (spinal cord and peripheral nerves).