The prototypic taxane paclitaxel, which disrupts tubulin dynamics, has been widely used in the treatment of solid malignancies. However, it has been associated with adverse cardiac effects. Therefore, the effect of the paclitaxel infusion on P wave duration and dispersion (PWD) was investigated. Twelve-lead surface ECG's were recorded twice from 12 patients with breast, ovarian and non-small-cell lung carcinoma: one just before paclitaxel infusion and the other 1 hour after the end of the infusion. The changes in maximum (Pmax) and minimum P wave duration (Pmin) were measured manually and the difference between the two values was defined as PWD. The mean heart rate, Pmin, did not change after the infusion. However, Pmax, PWD and the average P wave duration significantly increased after infusion (122 +/- 5 vs. 125 +/- 5 p = 0.001 and 46 +/- 7 vs. 53 +/- 9 p = 0.03,97 +/- 5 vs. 101 +/- 5 ms p = 0.02 respectively). We found that paclitaxel infusion increased PWD and this may be a result of the drug's effect on cardiac autonomic modulation.