Opportunistic infections often coexist with human immunodeficiency virus (HIV) infection in brain. Making the correct diagnosis is often difficult despite recent advances in neuroimaging techniques. 1H magnetic resonance spectroscopy (1H MRS) is an emerging non-invasive examination for diagnosis and monitoring of brain disorders. 1H MRS measures a variety of organic compounds using magnetism and radio waves. Biochemical aberrations in brain, not shown by conventional tests, may be demonstrated by 1H MRS testing. A patient coinfected with HIV and hepatitis B (HBV) presented with progressive dementia. Clinical, neuroradiological and cerebrospinal fluid (CSF) examinations failed to provide a diagnosis in support of either HIV-1-associated cognitive/motor complex or HBV-induced hepatic encephalopathy (HE), 1H MRS was used in an attempt to discriminate between these diagnoses. Spectroscopy demonstrated increased glutamine and normal N-acetyl aspartate (NAA) levels, metabolic changes consistent with HE. These findings were later confirmed pathologically. Proton magnetic resonance spectroscopy is a non-invasive test with utility for the differential diagnosis of HIV-associated dementia.