P2Y receptors are metabotropic G-protein-coupled receptors, which are involved in many important biologic functions in the central nervous system including retina. Subtypes of P2Y receptors in retinal tissue vary according to the species and the cell types. We examined the molecular and pharmacologic profiles of P2Y purinoceptors in retinoblastoma cell, which has not been identified yet. To achieve this goal, we used Ca2＋ imaging technique and western blot analysis in WERI-Rb-1 cell, a human retino</SUP>blastoma cell line. ATP (10ՌM) elicited strong but transient [Ca2＋]i increase in a concentration- dependent manner from more than 80% of the WERI-Rb-1 cells (n=46). Orders of potency of P2Y agonists in evoking [Ca2＋]i transients were 2MeS-ATP＞ATP＞＞UTP=ՁՂ-MeATP, which was compatible with the subclass of P2Y1 receptor. The [Ca2＋]i transients evoked by applications of 2MeS-ATP and/or ATP were also profoundly suppressed in the presence of P2Y1 selective blocker (MRS 2179; 30ՌM). P2Y1 receptor expression in WERI-Rb-1 cells was also identified by using western blot. Taken together, P2Y1 receptor is mainly expressed in a retinoblastoma cell, which elicits Ca2＋ release from internal Ca2＋ storage sites via the phospholipase C-mediated pathway. P2Y1 receptor activation in retinoblastoma cell could be a useful model to investigate the role of purinergic [Ca2＋]i signaling in neural tissue as well as to find a novel therapeutic target to this lethal cancer.