Since analysis of heart rate variability (HRV) is able to identify subjects at risk of sudden death and as antiarrhythmics can interfere with this prognosis, the objective of this study was to determine whether antiarrhythmics (AA) modified the HRV measured on a 24-hour Holter recording and after rapid ventricular stimulation and whether the initial HRV and its possible modification during treatment with AA were correlated with the results of AA treatment in patients with ventricular tachycardia (sustained VT). The HRV was studied in 50 patients with heart disease and spontaneous sustained VT, reproduced by programmed ventricular stimulation. This analysis was performed at baseline with antiarrhythmic treatment consisting of low-dose beta-blocker and quinidines in 26 patients (group I) or amiodarone in 24 patients (group II). Treatment was effective (i.e. prevented induction of VT) in 9 patients in group I (group la) and 5 patients in group II (group IIa). Treatment was ineffective in the other 17 patients of group I (group Ib) and 19 patients of group II (group IIb). The initial HRV was similar in the patients of groups Ia and Ib or groups IIa and IIb. Temporal analysis did not reveal any significant variation of HRV during AA treatment. In contrast, spectral analysis of HRV and the HRV observed during ventricular stimulation demonstrated a significant reduction of this parameter (p < 0.05 for groups I and II combined). IN CONCLUSION: the initial HRV is not predictive of the results of treatment. Quinidines and amiodarone tend to decrease HRV regardless of the effect of the AA on the prevention of VT.