La1-ySryFe1-xAlxO3-delta perovskites were studied as potential materials for solid-oxide fuel cell (SOFC) cathodes. The phase relations in the LaFeO3-SrFeO3-delta-LaAlO3 system were investigated by X-ray powder diffraction analysis. The defect structure of the La1-ySryFe1-xAlxO3-delta perovskites was investigated by Mossbauer spectroscopy and weight-loss analysis. Relations between the nonstoichiometry and the conductivity of the La1-ySryFe1-xAlxO3-delta perovskites were investigated. The incorporation of aluminum (x) into LaFe1-xAlxO3 was found to have no influence on the defect structure but to decrease the conductivity. The incorporation of strontium OI) into La1-ySryFe1-xAlxO3-delta promotes the formation of anion vacancies and Fe4+ that lead to higher conductivity.