Magnesium oxide (MgO) single crystals with an average size of 6 cm have been grown by an arc-fusion method. X-ray powder diffraction and ultraviolet transmittance spectra are used to characterize properties of the obtained MgO single crystals. In addition, an efficient method for the proper use of three electrodes is applied to reduce the number of bubbles in the obtained MgO sample, which allows us to gain optically transparent high-purity MgO single crystals. Our present work shows that the control of the temperature field of the whole system is crucial to grow high-purity MgO single crystals with large and super-large sizes. (c) 2005 Elsevier B.V. All rights reserved.