Carbon nanotubes (CNTs) are emerging as promising nanomaterials for biomedical applications. Due to their unique structural, mechanical and electronic properties, CNTs can be used as electrical interfaces with the brain in particular with neurons. CNT-based neural interfaces/electrodes have been employed in cell culture and in vivo; they offer advantages over standard metal-based electrodes in terms of monitoring and stimulation of neuronal activity. One of the challenges for interfacing brain and machine is the biocompatibility of the materials used for electrode construction. While CNTs appear biocompatible, the exposure limits have not been set thus far. An appropriate (inter)national standards/rules for the use of CNTs need to be established before CNT-based electrodes/devices can be used in human subjects.