For forensic and clinical toxicologic purposes, cannabis consumption is screened using easy-to-handle immunoassays. The sensitivity and specificity of these immunoassays have not yet been established in samples from volunteers receiving oral synthetic tetrahydrocannabinol or cannabis extracts using liquid chromatography-mass spectrometry/mass spectrometry as the reference method. Urine samples were collected in an open, randomized, single-center, three-period crossover study including 18 healthy male volunteers given either 20 mg synthetic tetrahydrocannabinol (Marinol) as a control substance or five different types of Cannabis sativa extracts.