Purpose: A novel family of directly-gated ATP-ion channels is emerging. Our goal is to clone, functionally express and characterise new members of this family (P2X purinergic receptors).Methods: Degenerate PCR and low-stringency screening of cDNA libraries was used to isolate new P2X cDNAs. Electrophysiological recordings were made in Xenopus oocytes or transiently transfected HEK293 cells. Tissue distribution was assayed by in-situ hybridisation, Northern blot and RT-PCR.Results: We have cloned several ATP-gated channels, including P2X3, P2X4, P2X5 and P2X6. These channels are, to varying degrees, Ca 2 + permeable, modulated by Zn 2 + and blocked by suramin and PPADS.Conclusions: P2X receptors are ubiquitously expressed. Novel toxins will help in defining roles for the members of this new family of channels.