Tracer diffusion of O-18 in dense, polycrystalline La1-xSrxCoO3 for x = 0.1 has been measured in the temperature range 400 to 600 degrees C and at 500 degrees C for x = 0.2 at an oxygen partial pressure of 1 x 10(5) Pa. Depth profiles were obtained by secondary ion mass spectrometry. The diffusion coefficient for La0.9Sr0.1CoO3 is given by D=(17-247) exp[(-232+/-8 kJ/mole)/RT] cm(2)/s. This value is several orders of magnitude lower than D extrapolated from the results for x = 0.2 measured in the 700-900 degrees C temperature range. One possible explanation for the discrepancy is that the two measurements reflect different diffusion paths. As expected, La0.8Sr0.2CoO3 exhibits a higher diffusivity at 500 degrees C than does La0.9Sr0.1CoO3.