Computer simulation techniques have been used to investigate the defect chemistry of perovskite-structured ionic conductors based upon AZrO₃ (A = Ca, Ba) and LaMO₃ (M = Sc, Ga). Our studies have examined dopant site-selectivity, oxide ion migration and dopant–defect association at the atomic level. The energetics of dopant incorporation in AZrO₃ show strong correlation with ion size. We predict Y³⁺ to be one of the most favourable dopants for BaZrO₃ on energetic grounds, which accords with experimental work where this cation is the commonly used acceptor dopant for effective proton conduction. Binding energies for hydroxy–dopant pairs in BaZrO₃ are predicted to be favourable with the magnitude of the association increasing along the series Y < Yb < In < Sc. This suggests that proton mobility would be very sensitive to the type of acceptor dopant ion particularly at higher dopant levels. Oxygen vacancy migration in LaScO₃ is via a curved pathway around the edge of the ScO₆ octahedron. Dopant–vacancy clusters comprised of divalent dopants (Sr, Ca) at the La site have significant binding energies in LaScO₃, but very low energies in LaGaO₃. This points to greater trapping of the oxygen vacancies in doped LaScO₃, perhaps leading to higher activation energies at increasing dopant levels in accord with the available conductivity data.