Chronic fatigue syndrome/myalgic encephalomyelitis (ME/CFS) is an unexplained multisymptom/multisystem disorder for which there are currently no validated treatments. The present exploratory clinical trial aims to advance our understand of the mechanisms of in situ GSH synthesis control through assessment of the response of brain GSH and plasma markers of oxidative stress to different doses of NAC in comparison to placebo, as a potential treatment for ME/CFS that would provide neuroprotection against oxidative stress by restoring cortical GSH reserves. If successful, this exploratory clinical trial would address a significant public health concern by shedding new light onto the mechanisms of action of NAC in brain GSH restoration, which could open a new avenue for the development of potentially effective treatments for a disorder, ME/CFS, that currently has none.