The oxygen nonstoichiometry, delta, of La1-xCaxCrO3-delta (x=0.1-0.3) was measured by means of thermogravimetry as a function of oxygen partial pressure, P(O-2), temperature, T, between 1073 and 1373 K, and the content of calcium, x. In any compositions, delta becomes larger and is getting closer to delta=x/2 with decreasing P(O-2). At the same P(O-2), delta of La1-xCaxCrO3-delta increases with increasing T and x. There is almost no difference in oxygen nonstoichiometry between Ca-doped lanthanum chromite and Sr-doped lanthanum chromite. Defect chemical analysis was performed taking defect interaction into consideration. The nonstoichiometry curves were reproduced well by the proposed defect model and the obtained thermodynamic parameters. The influence of defect interaction on defect formation energy can be mainly attributed to change in interatomic potential due to defect-induced lattice expansion. (C) 2004 Elsevier B.V. All rights reserved.