Electrode arrays are commonly used to study spatial patterns during ventricular fibrillation (VF) where the choice of spacing between electrodes is an important decision. The Nyquist criterion states that an electrode spacing smaller than half the smallest significant wavelength is required to avoid spatial aliasing. The authors select a minimum interelectrode spacing on the basis of band-limited wavenumber power spectra of high-resolution VF data. Data were simultaneously recorded from a square 11-11 array of unipolar electrodes spaced 0.28 mm part. 140 Wavenumber spectra were calculated using the zero delay wavenumber spectrum method. Insignificant power was associated with almost all wavelengths shorter than 2.8 mm, suggesting that, for unipolar electrodes, spacing of 1 mm is adequate to study early VF.