The use of gas chromatography-mass spectrometry (GC-MS) in forensic analysis is increasing. To exploit fully the capabilities of MS, labeled standards, that can be used to improve the performance of the quantitative analysis, and to increase accuracy and precision, are required. A series of deuterated internal standards, corresponding to the 2C-series of phenethylamine derivatives, including 4-bromo-2,5-dimethoxyphenethylamine-d 6 (2C-B), 4-chloro-2,5-dimethoxyphenethylamine-d 6 (2C-C), 4-iodo-2,5-dimethoxy-phenethylamine-d 6 (2C-I), 4-ethylthio-2,5-dimethoxy-phenethylamine-d 6 (2C-T-2) and 2,5-dimethoxy-4-n-propylthiophenethylamine-d 6 (2C-T-7), were synthesized. These deuterated compounds were used to analyze for the corresponding unlabeled compounds in urine. The analysis was performed using GC-MS, with the selected ion monitoring (SIM) technique, whereby good results were achieved.