Four different β-Si 3 N 4 ceramics with silicon oxynitrides [Y 1 0 (SiO 4 ) 6 N 2 , Yb 4 Si 2 N 2 O 7 , Er 2 Si 3 N 4 O 3 , and La 1 0 (SiO 4 ) 6 N 2 , respectively] as secondary phases have been fabricated by hot-pressing the Si 3 N 4 -Re 4 Si 2 N 2 O 7 (Re=Y, Yb, Er, and La) compositions at 1820 o C for 2h under a pressure of 25MPa. The oxidation behavior of the hot-pressed ceramics was characterized and compared with that of the ceramics fabricated from Si 3 N 4 -Re 2 Si 2 O 7 compositions. All Si 3 N 4 ceramics investigated herein showed a parabolic weight gain with oxidation time at 1400 o C and the oxidation products of the ceramics were SiO 2 and Re 2 Si 2 O 7 . The Si 3 N 4 -Re 4 Si 2 N 2 O 7 compositions showed inferior oxidation resistance to those from Si 3 N 4 -Re 2 Si 2 O 7 compositions, owing to the incompatibility of the secondary phases of those ceramics with SiO 2 , the oxidation product of Si 3 N 4 . Si 3 N 4 ceramics from a Si 3 N 4 -Er 4 Si 2 N 2 O 7 composition showed the best oxidation resistance of 0.198 mg cm - 2 after oxidation at 1400 o C for 192h in air among the compositions investigated herein.