Al-Fe-Si foils with an appropriate treatment exhibit, during bulge testing, different types of plastic instabilities. In the as-received foils only uniform straining is observed. Solution treatment at 590 degreesC for 30 min results in the appearance of a negative strain rate sensitivity and various types of instabilities. After instantaneous changes of the stress rate during bulging, significant instabilities on stress - strain curves appear as a result of pronounced strain rate oscillations. The amplitude of these oscillations decay with increasing time, and after a transient period, straining becomes uniform again. Spontaneous discontinuous yielding occurs in specimens annealed at 630 degreesC for 30 min. The main features of these instabilities are the presence of critical strains for the onset of oscillations, their existence in a limited range of strains and the presence of a negative strain rate sensitivity. These results are consistent with recent theoretical models derived for uniaxial straining. The differences in sample behavior in biaxial and uniaxial testing are discussed.