Ni-Al coprecipitated catalysts promoted with magnesium have been prepared using the rising and the constant pH techniques, two precipitant agents [(1) KOH and K2CO3, and (2) NH4OH)] and different metal contents. Catalyst characterization by temperature-programmed reduction and CO2 reforming of methane as a test reaction served to select the appropriate catalysts for use in the steam gasification of biomass. The catalysts selected were NiMgAl2O5, prepared at constant pH and precipitated with KOH and K2CO3; NiMgAl4O8 and NiMgAl1.24O3.86, both prepared at increasing pH with NH4OH. Biomass steam gasification experiments were carried out at 700 degreesC and at atmospheric pressure using different steam/biomass (S/B) and catalyst weight/biomass flow rate (W/B) ratios. From an analysis of the results obtained, the initial activity and stability of the catalysts have been studied. The NiMgAl2O5 catalyst presents the best performance showing the highest initial activity and stability. This work evidences an improvement of the NiMgAl2O5 catalyst with respect to the previously studied NiAl2O4 catalyst.