The effect of Thapsigargicin (TGC), a non-phorbol ester type tumor promoter, on Ca2+ movements has been investigated using L1210 mouse lymphoma cells. Ca2+ release from intact and digitonin permeabilized cells was evaluated using Fura-2 and Fura-3. TGC like Thapsigargin (TG) has the ability to discharge the intracellular Ca2+ stores and to increase intracellular free Ca2+ concentrations. TGC in a concentration dependent manner (0.16-16 nM) also inhibited cell growth and this effect was at least partially reversed by arachidonate.