Delayed aflerdepolarizations (DADs) may develop into triggered automaticity and ventricular arrhythmias. However, the potential role of DADs in the genesis of Ischemic arrhythmias is not clear. We studied the effects of different components of severe ischemia (acidosis, hypoxia, lactate, increased potassium, and the absence of glucose) on DADs. DADs were evoked using trains of 30–60 externally applied pulses at a rate of 4–5 Hz in the presence of isoproterenol (10-7 M) or dibutyryl cyclic 3′, 5′ adenosine monophosphate (dB-cAMP, 10-3 M). Acidosis, caused by the addition of protons (pH = 6.8), increased the amplitude of DADs from 3.2 ± 0.4 to 5.9 ±0.5 mV (n = 8, p < 0.001). DADs were abolished by hypoxia (pO2 < 35 mm Hg, n= 7, p < 0.001) from control values of 3.4 ±0.3 mV. DADs were also abolished by neutral lactate (20 mM, n=7, p < 0.001) in the absence of glucose. Acidotic lactate (20 mM, pH. = 6.8), however, was unable to abolish DADs. Increasing the extracellular potassium concentration to 16.2 mM decreased DAD amplitude from 3.6 ±0.27 mV to 1.3 ± 0.1 mV (n = 5, p < 0.002) with an associated reduction of membrane potential from −86.2 ± 0.9 to − 58.6 ± 0.9 mV. The overall effect of simulated ischemia (all components tested together) was to abolish DADs (n = 8, p < 0.001), with hypoxia as the most important factor. Neither the glycolytic inhibitors iodoacetate (0.1 mM) and 2-deoxyglucose (10 mM with 10 mM pyruvate) nor the absence of glucose changed the amplitude of DADs. 2-Deoxyglucose (10 mM) in the absence of pyruvate, cyanide (0.5–2.0 mM), and dinitrophenol (0.1–1.0 mM) each abolished DADs. We interpret these findings to mean that DADs are unlikely to occur in severe myocardial ischemia.