Cell death by apoptosis triggers the engagement of a conserved intracellular machinery of execution, involving mainly the activation of the caspase family of cysteine proteases. Caspase-3 is a common effector of most of the apoptotic pathways and is able to cleave several target proteins whose degradation will contribute to the execution phase of the cell demise program. Here we present a modification of the Western blot protocol to improve sensitivity of caspase-3 detection, providing a valuable tool to access its activation in biological specimens.