The novel cannabinoid receptor GPR55 is expressed by rodent islets and it has been implicated in β-cell function in response to a range of ligands. This study evaluated the effects of GPR55 ligands on intracellular calcium ([Cap>2+p>]i) levels and insulin secretion from islets isolated from GPR55 knockout (GPR55 p>−/−p>) mice, age-matched wildtype (WT) mice and human pancreas.