The syndrome of Jervell and Lange-Nielsen with its characteristic combination of Q-T-(U) abnormalities and recurrent episodes of ventricular tachycardia (VT) or ventricular fibrillation can serve as a model for establishing recycling excitation (re-entry) as the likely cause of VT. The ECG abnormality in the Q-T-(U) segment indicates the underlying asynchronous repolarisation, probably localized in the His-Purkinje system. Asynchronous delayed repolarisation facilitates re-entry excitations. A personal case is reported which demonstrated two different patterns of inducing premature beats and VT, indicative of two different fascicular pathways of circus movement. The inducing extrasystole determines the circuit pathway and thus the ECG pattern of VT. The VT shows a fixed time relation depending on conduction delay and refractory period, which is a further indication for an underlying re-entry mechanism. Spontaneous changes in time relation or morphology point toward alterations in circuit pathways and can terminate the VT. Clinical findings in three further cases of the syndrome are reported. Furthermore, the possible general significance of these findings is highlighted by the occurrence of the described phenomena in seven patients in whom Q-T-(U) abnormalities exist merely as transient symptomatic disturbances.