In the present study, the superplastic behavior of five Al-Mg-Zn alloys in coarse grain size condition has been studied. The alloys were melted, cast into ingots and hot rolled. The grain size of the rolled samples was 69, 45, 40, 30 and 35 mu m. Tensile test specimens were machined from the hot rolled plate in the rolling direction. Strain-rate-change (SCR) tests at temperatures between 300 and 450 degrees C and strain rates between 1 x 10(-)4 and 1 x 10(-1) s(-1) were carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation-to-failure tests were conducted at those temperatures and strain rates, where the alloys showed high strain rate sensitivity. A maximal elongation of 400% was obtained for the 3.89 wt.% Zn alloy. The results are explained in terms of solute drag creep as the principal deformation mechanism.