The performance of single-cell planar solid oxide fuel cells using coal syngas, with and without hydrogen sulfide (H2S), was studied. A state-of-the-art gas delivery system, data acquisition system, and test stand were designed and assembled for experimentation. All cells were tested at 850 °C with a constant current load of 14.3 A (current density of 0.20 A cm-2). The results from using syngas with no H2S indicated no degradation after 290 h of operation. After immediately injecting CO (and water) in the H2-N2 mixture, there was a slight tendency of improving performance (power) and then the behavior remained steady. On the other hand, results for the test with syngas in the presence of H2S (200-240 ppm) indicated good performance over 570 h (650 h total operation time) with 10-12.5% degradation. The results suggest these cells can be used for extended periods of time for syngas applications, and in the presence of H2S the cells show no major degradation. © 2005 Elsevier B.V. All rights reserved.