0.15 wt% Ni/x wt% Ln/Al2O3 (x=0, 1.7, 8.5, Ln=rare earth mixture) catalysts have been tested for life time stability (60-600 h) during CO2 reforming of methane in a fluidized bed reactor at 800 degrees C and 1 atm with CH4:CO2:N-2=2:2:1. The catalyst with 1.7% Ln is more active and stable than the unpromoted catalyst and the catalyst with 8.5% Ln. Samples of the catalysts were taken out after different times on stream and characterized using magnetic measurements and Transmission Electron Microscopy (TEM). The characterization results showed that even after prereduction at 1000 degrees C (5% H-2/He, 2 h), Ni is continuously reduced during testing of the Ln-containing catalysts. This effect is more pronounced at higher Ln loadings (8.5% vs. 1.7% Ln). An increase in Ni particle size during testing was also observed. The results indicate that Ni sintering is initially a major reason for deactivation, while coking becomes increasingly important with longer times on stream (i.e., >60 h). The catalyst with 1.7% Ln has a higher initial Ni dispersion than the catalyst with 0% Ln. The higher activity of the promoted vs. unpromoted catalyst cannot be fully explained by this difference. However, the activity difference between the catalyst promoted with 1.7% or 8.5% Ln may be explained by a lower reduction of Ni for the 8.5% Ln-promoted catalyst.