More than 80 variants of glucose-6-phosphate dehydrogenase (G6PD) are associated with chronic nonspherocytic haemolytic anaemia (CNSHA); however, the molecular basis of this association is not fully understood. We have used the polymerase chain reaction and nucleotide sequence analysis to characterize a new G6PD variant, which we designate as G6PD Bari, in a G6PD-deficient boy affected by CNSHA. A single mutation leading to an amino-acid substitution was detected in the G6PD coding region, viz. a C->T transition at position 1187 predicting leucine at residue 396 in the enzyme; proline is invariably present in evolutionary distant G6PD molecules at this position. Inheritance in the patient's family was demonstrated by the polymerase chain reaction followed by diagnostic restriction enzyme analysis. The C->T transition responsible for G6PD Bari maps close to several other mutations previously identified in G6PD variants associated with CNSHA.