Solid oxide fuel cells (SOFCs) consisting of an 8 mol % Y-stabilized ZrO2 (YSZ) electrolyte, La(0.8)Sr0(.2)MnO(3)-YSZ(LSM-YSZ) cathode, and Ni-YSZ anode support were operated directly using isooctane. The electrical performance of SOFCs operating with 5.3 vol % C8H18 in N-2 was measured over a temperature range of 600-775 degrees C. Open-circuit voltages achieved slightly over 1 V. The maximum power densities attained were 0.10 and 0.24 W/cm(2) at 650 and 700 degrees C, respectively. Mass spectroscopy analysis showed C8H18 thermally decomposed largely into ethylene and methane, which suggested SOFC fuel reactions primarily, involved these gas species.