Hexabenzylhexaazaisowurtzitane (HBIW), m.p. 152-155.5 degrees C, was synthesized in reaction of glyoxal with PhCH2NH2 (I) carried out at pH 10 and 25-70 degrees C for 12 h in H2SO4-MeOH system. Effects of time, temp., the H2SO4 catalyst and I concns. and the rate of the glyoxal dropping in were studied. The highest HBIW yield (67%) was achieved after 9 h at 60 degrees C, the H2SO4-I, H2O-MeOH and I-MeOH ratios 0.08, 0.1 and 0.2 resp. when glyoxal was dropped-in for 1 h.