Scratch-pad memories (SPM) are small on-chip memory devices whose access is much faster and consumes much less energy than off-chip memories. While SPM are usually too small for containing all the code or data of an application, significant energy consumption reductions can be achieved by assigning to them memory objects which are often accessed. The stack is one of the most frequently accessed data memory object, but its dynamic behavior makes it difficult to place into the SPM. This paper presents a simple and practical technique for placing frequently accessed parts of the stack into the SPM. The technique has been designed for multi-task environments where the SPM is shared among several tasks. Results show that the proposed technique achieves energy reductions which are comparable to ones obtain by other techniques supporting only single-task applications.