A sensitive and specific LC-MS/MS method for the quantification of the endocannabinoids and related structures anandamide, 2-arachidonoyl glycerol, 2-arachidonyl glycerol ether, O-arachidonoyl ethanolamide, dihomo-gamma-linolenoyl ethanolamide, docosatetraenoyl ethanolamide, N-arachidonoyl dopamine, N-arachidonyl glycine, N-oleoyl dopamine, oleoyl ethanolamide, palmitoyl ethanolamide, and stearoyl ethanolamide in human plasma was developed and validated. Compounds were extracted using acetonitrile followed by solid-phase extraction. Separation was performed on a Xterra C8 column using gradient elution coupled to a triple-quadrupole MS. LLOQ levels ranged from 0.02 to 1.75 microg/mL, LODs ranged from 0.0002 to 0.1266 ng/mL, and accuracies were >80% (except stearoyl ethanolamide at lowest spike level) at all spike levels.