OBJECTIVE--To examine left and right ventricular contraction in Romano-Ward syndrome: does abnormal myocardium affect the predisposition to arrhythmia? DESIGN--Tomographic radionuclide ventriculography was performed after the red blood cells were labelled conventionally with stannous pyrophosphate and technetium-99m. SETTING--Department of Nuclear Medicine, Aberdeen Royal Infirmary. PATIENTS--Eight subjects from two families known to have Romano-Ward syndrome, four of whom (two from each family) had had symptoms. RESULTS--The five subjects from family 1 had normal left ventricular contraction; two had subtle abnormalities of right ventricular phase. in family 2 all three subjects had abnormal left ventricular contraction (reduced amplitude in three, abnormal phase in two). All had subtle abnormalities of right ventricular phase. CONCLUSION--Abnormal right or left ventricular myocardium may be partly or wholly responsible for the repolarisation changes seen on the electrocardiogram of these families or may act as an ectopic focus to start ventricular tachycardias in a susceptible heart.