Si3N4/SiC composite ceramics were hot-pressed in order to investigate the crack-healing behavior under stress. Semi-elliptical surface cracks of 100 mu m in surface length were made on each specimen. The pre-cracked specimens were crack-healed under cyclic or constant bending stress, and the resultant bending strength and cyclic fatigue strength were studied. The threshold stress for crack-healing was investigated at healing temperatures of 1000 degrees and 1200 degrees C. The cyclic fatigue strengths of crack-healed specimens were also investigated at healing temperatures of 900 degrees and 1000 degrees C. The main conclusions are as follows: (1) The threshold cyclic and constant stresses for crack-healing, below which pre-cracked specimens recovered their bending strength, were 300 MPa, which was 75% of the bending strength of the pre-cracked specimens and (2) the crack-healed specimens exhibited quite high cyclic fatigue strength at crack-healing temperatures of 900 degrees and 1000 degrees C.