Affinities and efficacies of several reference cannabinoid ligands were investigated at central and peripheral cannabinoid receptors in three different species (rat, mouse, and human). The tested compounds belong to different chemical classes such as classical and non-classical terpene derivatives (Δ 8 -THC, Δ 9 -THC, HU 210, CP 55,940, CP 55,244, CP 55,243 and CP 47,947), aminoalkylindole (WIN 55,212-2, WIN 55,212-3) and diarylpyrazole cannabinoids (SR 141716A, SR 144528). As cannabinoid receptors have been shown to be mainly coupled to Gi/o type G- proteins, and by using the [ 35 S]-GTPγS nucleotide binding modulation, we characterized the functional activity of these ligands which can act as agonists (positive intrinsic activity), partial agonists (partial positive intrinsic activity), antagonists (no intrinsic activity), or inverse agonists (negative intrinsic activity). To our knowledge, some derivatives (Δ 8 -THC, WIN 55,212-3, CP 55,243 and CP 47,947) have never been characterized in [ 35 S]-GTPγS binding assays and up to now, this study represents the largest survey of reference cannabinoids performed in unique experimental conditions and in the same laboratory.