A modified thermal analysis procedure was used to study the heat released during the combustion of magnesium alloys in air. Magnesium and magnesium alloys were heated to 1000 K under giving amounts of air and relative humidity. For the pure magnesium, the maximum enthalpy release occurred at temperature of 908.5 K. For the Mg-xCa alloys, increasing the Ca content, x from 1 to 3%, lifted the peak temperature from 918 to 924 K. For the Mg-5Ca alloy, the heated cake showed ignition-proof up to 1000 K. The peak temperature of the as-received AZ series alloys decreased greatly as Al content increased; while for the solution-treated alloys, the peak temperature was significantly raised. For the solution-treated AZ91 alloys, the heated cake remained ignition-proof up to 1000 K. (C) 2004 Elsevier B.V. All rights reserved.