One of the main functions of L-arginine (ARG) is the synthesis of nitric oxide (NO). NO is an important regulator of physiological processes in the central nervous system (CNS). NO promotes optimal cerebral blood flow, consolidates memory processes, facilitates long-term potentiation, maintains sleep-wake cycles, and assists in normal olfaction. However, at pathological levels, NO adversely affects brain function producing nitroxidative stress and promoting development of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and other disorders of the CNS. This review summarizes current knowledge of the role of NO in the CNS and the role of diet in regulating the levels of NO.