Partial electronic conduction in Ni-doped LaGaO3-based oxide was investigated by using the ion-blocking method. It was seen that the hole and the electronic conduction originated from doped Ni becomes dominant with decreasing temperature and also with increasing Ni content. Po-2 dependences of hole and electronic conduction decrease with increasing Ni content and it becomes almost Po-2(1/12) and Po-2(-1/12), respectively, at 1073 K when 10 mol% Ni is doped to Ga site. The estimated transport number of oxide ion in Ni-doped LaGaO3 is always hi-her than 0.95 in Po-2 range from 1 to 10(-21) atm, which is the important Po-2 range for fuel cell application. Therefore, the main charge carrier is still oxide ion in Ni-doped LaGaO3. Comparing with the partial electronic conduction in Co-doped sample, the electrolyte domain is wider on Ni-doped sample. (C) 2004 Elsevier B.V. All rights reserved.