Despite the experimental evidence of significant biological effects of extremely low frequency (ELF) magnetic fields (MFs), the underlying mechanisms are still unclear. Among the few mechanisms proposed, of particular interest is the so called “ion parametric resonance (IPR)” hypothesis, frequently referred to as theoretical support for medical applications. We studied the effect of different combinations of static (DC) and alternating (AC) ELF MFs tuned on resonance conditions for potassium (K+) on TEA-sensitive voltage-dependent outward K+ currents in the human neuroblastoma BE(2)C cell line. Currents through the cell membrane were measured by whole-cell patch clamp before, during, and after exposure to MF. No significant changes in K+ current density were found. This study does not confirm the IPR hypothesis at the level of TEA-sensitive voltage-dependent outward K+ currents in our experimental conditions. However, this is not a direct disprove of the hypothesis, which should be investigated on other ion channels and at single channel levels also. Bioelectromagnetics 34:579–588, 2013. © 2013 Wiley Periodicals, Inc.