The macaque monkey is exceptional in its ability to perform complex cognitive tasks, making it particularly well suited to study the detailed neural mechanisms of high-level cognitive functions. Recently, there has been somewhat of a revolution in optical neuroimaging techniques, in particular multi-photon imaging combined with activity dependent fluorophores. It would be very relevant for cognitive neuroscience to apply these techniques to macaque monkeys. However, 2-photon microscopy is not powerful enough to image through primate meninges (the protective layers of tissue that cover the brain). Therefore, we have developed a 3-photon microscope to allow reliable and long-term imaging in awake and behaving macaque monkeys. Furthermore, we have developed viral injection techniques to obtain large and homogenous expression of functional indicators. This setup now allows us to reliably image the vascular bed as well as neuronal activity in macaque monkey cortex.