Recent advancements in proton magnetic resonance spectroscopy (1H-MRS) have significantly enhanced our understanding of brain function. This chapter reviews studies on1H-MRS of obsessive-compulsive disorder (OCD), focusing on excitatory (glutamate, Glu) and inhibitory (gamma-aminobutyric acid, GABA) neurotransmitters, thought to be involved with the brain circuitry behind the disease, although the technique is not yet implemented in clinical practice. This chapter starts by presenting basic1H-MRS and OCD concepts, and then it reviews the1H-MRS studies on OCD, highlighting the roles of Glu and GABA, but also commenting on other neurometabolites, as N-acetyl aspartate and choline. Although most studies show no abnormalities, some found lower GABA in cingulate cortex and higher choline in thalamus in OCD. In the final section, future challenges and directions are discussed, such as the need to improve1H-MRS technology, to standardize1H-MRS protocols, to obtain larger sample sizes, and to conduct meta-analyses to better understand neurometabolic changes in OCD.