［Ca²⁺］_i transients were induced in porcine polymorphonuclear leukocytes in response to ATP and ADP, while no evident change in ［Ca²⁺］_i was observed after AMP addition. The cells showed varied dose dependency upon ATP and ADP. In the Ca²⁺-free bath solution, ATP and ADP could still cause ［Ca²⁺］_i elevation in the cells. The results showed that the P2 receptors are present on porcine polymorphonuclear leukocytes and should belong to the P2Y subclass of purinoceptor family.