Herein a method was develop and validated for the detection and quantification of five new psychoactive substances (NPS) belonging to three categories: synthetic cathinones (mephedrone, 3,4-MDPV), opioids (AH-7921) and cannabinoids (JWH-018, AM-2201) by EI GC-MS. Target analytes were quantified in whole blood; in urine the same compounds plus methylone were detected. Liquid-liquid extraction by MTBE – butyl acetate (1:1, v/v) in blood and butyl acetate in urine was applied for the recovery of analytes, while no derivatization was necessary for their sensitive detection and quantification. The method showed good linearity for all analytes within a concentration range from 0.25 to 2 μg/mL for mephedrone, from 0.02 to 0.16 μg/mL for 3,4-MDPV and AH-7921 and from 0.005 to 0.04 μg/mL for JWH-018 and AM-2201. LOD ranged from 0.002 μg/mL (JWH-018 and AM-2201 in blood and urine), to 0.08 μg/mL (mephedrone in urine). LOQ in blood ranged from 0.005 μg/mL for JWH-018 and AM-2201 to 0.25 μg/mL for mephedrone. Accuracy was within acceptable limits with % bias ranging from +20% to -17.98% for intra-assay study and from +18.87% to -11.16% for inter-assay study. Precision was found to be between 2.60% and 17.17% (CV%) for intra-assay study and from 6.03% to 13.72% (CV%) for inter-assay study. An intra laboratory comparison provided proof of the method robustness. The developed method can be used for the reliable and fast quantification of five NPS in blood and the detection of six NPS in urine within the practice of a clinical or forensic toxicology laboratory.Copyright © 2020 Elsevier B.V. All rights reserved.