A series of hollow biodegradable polymeric microcapsules were prepared, of which their susceptibility to ultrasound was used for triggered release. High speed imaging of the ultrasound experiments showed a strong correlation between the acoustic pressure needed to activate these microcapsules and their shell thickness to diameter ratio. Based on this information a selective triggering of capsules with two different shell thickness to diameter ratios was successfully performed. The capsules were mixed in a single system and were activated independently from each other by a differentiation in acoustic pressure levels. This application is of great interest in the field of drug delivery, since this system allows for localized multiple drug releases in a selective fashion.