Reduction of doped lanthanum chromite results in a linear expansion of the sample depending on dopant concentration, temperature, and oxygen content within the sample. In order to elucidate the defect structure of the perovskite-type oxide solid solution La1-xCaxCrO3-delta (x = 0.10 and 0.20), the nonstoichiometry delta was measured as a function of oxygen partial pressure from 900 to 1100 degrees C by means of a thermogravimetric method. The thermal expansion in reducing environments was measured as a function of oxygen partial pressure at 1000 degrees C and then related to the change in oxygen stoichiometry. A linear correlation between thermal expansion and oxygen nonstoichiometry was found.