The effect of intramuscular arteether (150 mg daily for 3 days) on electrocardiogram was studied in 16 patients having falciparum malaria. This included three patients with cerebral malaria, three patients with jaundice (S. bilirubin > 3 mg per cent) and ten patients with uncomplicated malaria. Five patients had tachycardia prior to arteether treatment. The mean RR interval before starting the treatment was 0.59 sec which increased progressively--0.60, 0.68 and 0.69 sec on Day 1, 2 and 3 respectively after starting the treatment. There was no significant difference statistically in the mean corrected QT interval (p > 0.05), PR interval (p > 0.05), QRS duration (p > 0.05) and diastolic BP (p > 0.05) before starting and at the end of treatment on Day 3. One patient had developed first degree heart block (PR 0.24), while another patient had prolonged QTc (0.48 sec) on Day 3. Subsequent ECG of both these patients was normal on Day 5. The profile of ECG changes was same in the patients of uncomplicated and complicated malaria. Absence of any significant effect on BP and ECG changes precludes the significant effect of arteether on the cardiovascular system when compared to quinine which may cause hypotension, arrhythmia and QTc prolongation.