Gamma-Hydroxybutyrate (GHB), a naturally-occurring substance acting similarly to some neurotransmitters in the mammalian brain, is becoming a popular recreational drug due to sedative and anesthetic effects.Furthermore, illicit GHB and its analog precursor gamma-butyrolactone (GBL) have recently been suspected for use as date rape pill, the forensic discrimination of endogenous GHB/GBL from exogenous origin in human urine is in need.We proposed an integrated approach based on GC-MS impurity profile and GC-IR(isotope ratio)MS carbon isotopic ratio (δ13C) method.The method was tested on 25 healthy volunteers (12 male and 13 female, aged 25-35 years) to evaluate its feasibility.