The stress and ductility of some commercial aluminum alloys (1050, 3003, 3004 and 5182) have been investigated as a function of strain rate over the range from 1×10-3 to 3×103s-1 at room temperature. The nominal stresses at a strain of e=0.105 for both 1050 and 3003 alloys increase with increasing strain rate, but the nominal stresses for both 3004 and 5182 alloys decrease with increasing strain rate in the low and intermediate ranges from 1×10-3 to 1×102s-1. The alloys showing the above negative strain rate sensitivity of stress in this strain rate range contain magnesium atoms in solute. Therefore, this behavior of stress in these alloys is possibly related to the interaction between magnesium atoms in solute and dislocations. Uniform elongations of alloys except a 1050 alloy show the maximum values in an intermediate strain rate range. Total elongations increase with increasing strain rate for all alloys investigated.