OBJECTIVE: To investigate the relationship between cognitive impairment and 1H magnetic resonance spectroscopy (1H MR spectroscopy) in patients with subarachnoid hemorrhage (SAH) caused by rupture of middle cerebral artery (MCA) aneurysm. METHOD: 1H MR spectroscopy was performed in 6 patients with SAH after rupture of MCA aneurysm and in 20 controls. Image-guided localized 1H MR spectra were obtained from left parietal white matter (PWM). The cognitive status was evaluated using the Mini Mental Status Examination (MMSE), and the scores were correlated with N-acetyl aspartate/creatine (NAA/Cr), choline/creatine (Cho/ Cr), and myoinositol/creatine (mI/Cr) metabolic ratios. RESULTS: NAA/Cr was significantly lower, and Cho/Cr was higher in SAH patients than in controls in the left PWM (p<0.05). NAA/Cr in the left PWM was correlated with MMSE (p<0.05), but Cho/Cr and mI/Cr in the left PWM was not correlated with MMSE (p>0.05). CONCLUSION: 1H MR spectroscopy could be helpful in the evaluation of cognitive impairment in SAH.