Summary. A cohort of 121 patients with B-cell chronic lymphocytic leukaemia (B-CLL) was investigated for a single nucleotide polymorphism in the P2X7 receptor gene (1513 A→C), and the findings were correlated with clinical prognostic markers, in vitro sensitivity to fludarabine, expression of Bcl-2 family proteins and overall survival. The frequency of the polymorphism in B-CLL samples was not significantly different from that found in normal healthy controls (P = 0·27; Fisher's exact test). Furthermore, when the B-CLL patients were analysed according to P2X7 genotype (1513 A/A versus 1513 A/C), there was no significant difference in age at diagnosis, stage at diagnosis, lymphocyte doubling time, time to first treatment, progression-free survival and overall survival, and neither was there any evidence of bias in terms of VH gene mutational status, CD38 expression, in vitro sensitivity to fludarabine or expression of Bcl-2, Bax or Mcl-1 between the two groups. These results indicate that the 1513 A→C polymorphism of the P2X7 gene is unlikely to play a significant role in the pathogenesis or disease progression of B-CLL.