The influence of the fuel composition and fuel utilisation on the performance oi an anode-supported solid oxide fuel cell (SOFC) have been studied as function of time by DC-methods both on single cells and on short stacks. For a single cell the influence of the water/hydrogen ratio in the fuel can mainly be attributed to the change in the open cell voltage. The performance of single cell fed with a mixture of methane and water (1:2) (internal reforming) is in the current density range up to 0.3 A/cm(2) comparable to the performance of the cell under hydrogen/water (2:1) having the same open cell voltage. The influence of the water content in the hydrogen an the performance of a short stack is also mainly caused by the difference in open cell voltage. The influence of a prolonged galvanostatic load on the performance of a short stack was measured. A shed stack driven at 375 mA/cm(2) and 800 degrees C or 1000 h (fuel H-2/H2O = 99:1 fuel utilisation 9%) showed an ageing of 64 mu Omega.cm(2)/h. This value is typical for these anode-supported cells under these conditions. A stack running under high humidity (H-2/H2O = 1:1) last 53 mV during the first 100 h of operation. After this period the stack voltage increased to values comparable to the starting values.