A 38-year-old male was arrested 7 times over an 8-month period for driving under the influence (DUI) of drugs. In each incident, gamma-hydroxybutyrate (GHB) was determined to be the causative agent. A blood specimen was drawn between 1.5 and 2.5 h after first police contact in each arrest. GHB was analyzed by gas chromatography-mass spectrometry, following extraction from blood using ethyl acetate and subsequent derivatization using BSTFA/TMCS. Blood GHB concentrations ranged from 44 to 184 mg/L (N = 7, mean 100 mg/L, median 73 mg/L). Overall signs of impairment included erratic driving (severe lane travel, collisions, and near-collisions), slurred speech, disorientation, slow to react, shaking, agitation, unable to focus, poor coordination and balance, poor performance in field sobriety tests, somnolence, and unconsciousness. On only one occasion were other drugs present in the subject's blood (thiopental and diazepam), which may have contributed to the observed driving impairment. During several police interviews, the subject stated he was addicted to GHB and gamma-butyrolactone (GBL), and admitted to previously taking "RenewTrient", "Dream On", "V35", "fitness supplements", and/or "GBL". During the same period as his DUI arrests, the subject had been admitted at least six times to different hospitals for GHB/GBL intoxications.