We investigated the influence of N-2 pressure control on the growth of bulk GaN crystals by using a Na flux. GaN single crystals with a maximum dimension of 3 mm could be obtained by this method, though smaller crystals of 0.5-2 mm in size have been grown without pressure control. This Suggested significant effects of additional NH3 gas on growth of GaN crystals in the Na flux method. (C) 2002 Published by Elsevier Science B.V.