Superplasticity at a high strain rate of 1.4x10(-1)s(-1) was exhibited at 783K in the powder metallurgy processed Al-16Si-5Fe-1Cu-0.5Mg-0.9Zr (wt%) alloys with and without 5 wt% addition of SIC particulates. The maximum elongations of 350% and 270% were obtained for the monolithic and composite material, respectively, where high m values were found. The high strain rate superplasticity in these materials was attributed to the presence of a thermally stable fine microstructure and the operation of grain boundary sliding. The lower superplastic elongation of the composite specimen compared to that of the monolithic specimen was suggested to the result of an increased density of cavities owing to the SiC decohesion at the SiC/matrix interface.