Abstract: High-frequency irreversible electroporation (H-FIRE) is an electroporation-based therapy used to ablate cancerous tissue. Treatment consists of delivering short pulses in a series of bursts. Reducing pulse duration leads to reduced treatment volumes compared to traditional IRE, therefore larger voltages are typically applied to generate ablations comparable in size. Administration of adjuvant calcium enhances ablation area in vitro for H-FIRE treatments of several pulse durations. Furthermore, H-FIRE treatment delivered with CaCl2 results in cell death thresholds higher than that of H-FIRE without calcium and comparable to IRE thresholds without calcium. Quantifying the reversible electroporation threshold revealed that CaCl2 enhances the permeabilization of cells compared to a NaCl control. H-FIRE treatment with calcium enhances the IRE to thermal cell death ratio, thereby also enhancing the positive immune response from treatment.