Women have a higher risk of developing torsade de pointes under OT-prolonging conditions. The electrophysiological differences between the sexes that could account for this are largely unknown. The objective of the work was to evaluate gender differences in repolarisation potentials using a method that is independent of the specific electrical properties of the thorax. 1410 normal recordings from the Glasgow 12-lead ECG database and 52 normal ECG maps obtained separately in Milan were analysed. The average difference between 1 and the correlation coefficient of the instantaneous pattern at the peak of T with that at every other instant is called the early repolarisation deviation index (ERDI) for J-T peak and the late repolarisation deviation index (LRDI) for T peak-T end. In standard ECG recordings, the ERDI was 0.42 +/- 0.22 in females compared with 0.19 +/- 0.16 in males (p < 10(-6)). The LRDI was higher in males under the age of 50. In body surface maps, the ERDI was 0.32 +/- 0.21 in females against 0.16 +/- 0.17 in males (p < 0.01), and the LRDI was non-significantly higher in males. The pattern of instantaneous body surface potentials showed gender differences during repolarisation with a method that is independent of the electrical properties of the thorax.