In this paper we report an investigation of proton conduction in two gallate systems, La1-xBa1+xGaO4-x/2 and La1-xSr2+xGaO5-x/2, containing tetrahedral Ga. Measurements in dry atmospheres show that both systems exhibit a p-type contribution to the conductivity, while a comparison between dry and wet atmospheres shows evidence for proton conduction. The La1-xBa1+xGaO4-x/2 system shows the highest proton conductivities, with conductivities reported being significantly higher (approximate to 1 X 10(-4) S cm(-1) at 500 degrees C for x = 0.2) than those for other structures containing tetrahedral ions, e.g. LaPO4. Replacement of La by Pr in this system leads to an increase in the electronic contribution to the conductivity. (c) 2005 Elsevier B.V. All rights reserved.