This study was undertaken to determine the effects of glucose, antioxidants and different oxygen tensions on the development of bovine embryos cultured in modified synthetic oviduct fluid (m-SOF) medium. In vitro matured (IVM) and fertilized (IVF) oocytes were incubated for 48 h. Embryos reaching at least the 4-cell stage were selected for further culture under various conditions for 6 d. Supplementing the m-SOF media with 4.5 mM glucose resulted in a significantly lower (P<0.01) embryo developmental rate (21 %; Day 8) than was obtained with 1.5 mM glucose (58 %; Day 8) or no glucose (53 %; Day 8). Antioxidants such as SOD, catalase and mannitol had no positive effect on embryo development in m-SOF medium supplemented with 1.5 mM glucose. However, in m-SOF medium supplemented with 4.5 mM glucose, SOD and mannitol significantly (P<0.05) improved embryo development: SOD increased the developmental rate from 19 to 35 % (Day 8), while mannitol increased it from 13 to 30 % (Day 8). Low oxygen concentration improved embryo development significantly (P<0.05) in m-SOF medium supplemented with 4.5 mM glucose (low O-2: 31 % vs high O-2: 14 %; Day 8) but not 6 mM glucose (low O-2: 58 % vs high O-2: 55 %; Day 8). Our data suggest that low concentration of glucose during culture of bovine embryos is beneficial, and that generation of free oxygen radicals is partly caused by a high concentration of glucose in the medium. (C) 1998 by Elsevier Science Inc.