Five high affinity G-protein-coupled receptors for sphingosine 1-phosphate (S1P) have been characterised so far (S1P 1 , 2 , 3 , 4 , 5 formerly referred to as edg1,5,3,6,8). In this study, we show that S1P, dihydro-sphingosine 1-phosphate (dihydro-S1P) and dioleoylphosphatidic acid (doPA) are agonists for the orphan receptor GPR63. All three phospholipids mobilise intracellular calcium in CHO cells transiently transfected with GPR63. Calcium signals required cotransfection of a chimeric Gα q / i protein in a fluorometric imaging plate reader (FLIPR ) assay but did not require overexpressed G proteins in an aequorin assay, using a green fluorescent protein (GFP)-aequorin fusion protein as a bioluminescent Ca 2 + reporter. GPR63 expression in CHO cells confers proliferative responses to S1P in a pertussis toxin (PTX)-insensitive manner. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) indicated highest expression in brain, especially in the thalamus and the nucleus caudatus. In peripheral tissues, highest expression was observed in thymus, stomach and small intestine; lower abundance of transcripts was detected in kidney, spleen, pancreas and heart. The discovery that S1P, dihydro-S1P and dioleoylphosphatidic acid activate GPR63 will facilitate the identification of agonists and antagonists, and help to unravel the biological function of this receptor.