We used principal components analysis (PCA) to quantify right ventricular (RV) repolarisation dispersion during diagnostic ajmaline test for suspected Brugada syndrome (BS). 10-second 15-lead electrocardiograms (ECG) (500 Hz, 12 standard leads + V1 to V3 from 3 rd intercostal space, V1h to V3h) were acquired in 61 patients (pts) with suspected BS (38 men, age 39±17 years) during ajmaline administration. PCA (ratio 2 nd /1 st eigenvalue) was performed on the J-T end interval using a) leads V1 to V3 (PCA stand ), b) V1h to V3h (PCA high ) and c) V1 to V3 + V1h to V3h (PCA total ). Pts with positive tests (n=20) had significantly higher PCA high and PCA total , on pre-test ECGs than those with negative tests. The maximum drug-induced increase of PCA was significantly greater in pts with positive than in those with negative tests (e.g. PCA high 6406±12622% vs 192±350%, p=0.004). Assessment of RV repolarisation dispersion using PCA can help the diagnosis of BS.