Organophosphates cause poisoning as a result of the excessive accumulation of acetylcholine at the cholinergic synapses due to inhibition of acetylcholinesterase (ChE). In the literature, it has been reported that there have been electrocardiographic abnormalities, including QT-interval prolongation in most patients with acute organophosphate poisoning (OPP), and a relation between blood ChE level and clinical severity in acute OPP. The aim of this study is to assess the relationship between blood ChE level and QTc interval in the patients with acute OPP. This retrospective study consists of 20 patients admitted to the emergency intensive care unit. A total of 93 QTc interval and blood ChE measures obtained on the same day from 20 cases were compared for their correlation. There were prolonged QTc intervals in 35.4% of the ECGs. There was a negative correlation between QTc interval and blood ChE measures. In following up the patients with acute OPP, QTc interval may be useful when blood ChE levels are low and may provide complementary information concerning the severity of poisoning. However, further prospective studies, supporting the present results, are needed.