The P2X7 receptor, a plasma membrane ATP-gated ion channel that plays a role in lymphocyte apoptosis, has been suggested as an important contributory factor to the pathogenesis of chronic lymphocytic leukaemia (CLL). The P2X7 gene resides on chromosome 12 and is polymorphic in the population at large (1513A/C) with the A and C alleles encoding fully active and nonfunctional proteins, respectively. We have evaluated the significance of this polymorphism by genotyping 144 patients with CLL and 348 healthy controls using a tetraprimer ARMS assay. We found no significant difference in allele frequency between patients and controls. Although patients with the C allele (A/C heterozygotes or C/C homozygotes) had a marginally shorter survival than those who were homozygous for the A allele, this difference was not significant for either the patient group considered as a whole or for IgVH-mutated/unmutated subsets. Finally, no association was found between trisomy 12 and P2X7 genotype. We conclude that the influence, if any, of P2X7 genotype on susceptibility to CLL or clinical outcome is small.