The superplastically formable aluminium alloy AA5083 has good weldability, reasonable corrosion resistance and strength. In order to test the formability of this alloy, blanks were formed by pressuzised gas into cones at constant strain rates. For this, a new analytical model was developed. The cone-cup testing method has been used to study the influence of a pulsating strain rate on the formability of this aluminium alloy. The forming operations were performed using an in-house designed and built equipment for superplastic matrices forming. The process was also modelled using a finite element code. Preliminary results are presented.