LaCoO3 and La0.8Ca0.2CoO3 ceramics show a nonelastic stress-strain behavior during four-point bending experiments where hysteresis loops are observed during loading-unloading cycles. Permanent strain is stored in the material after unloading, and a mechanism related to ferroelastic domain switching in the rhombohedral perovskite is proposed. Domain switching in the materials has been confirmed using X-ray diffractometry. Fracture toughnesses of La0.8Ca0.2CoO3 measured using single-edge notched beam and single-edge V-notched beam methods coincide and are equal to 2.2 MPa(.)m(1/2) at room temperature and decrease to similar to 1 MPa(.)m(1/2) at temperatures > 300 degreesC. A decrease in fracture toughness is consistent with ferroelastic behavior, because the rhombohedral distortion decreases with increasing temperature.