In acute heart failure syndrome (AHFS), dyspnea is one of the most common but least understood presenting symptoms for hospitalization. For this reason, dyspnea relief is increasingly becoming a focus in the development of therapies for the treatment of AHFS, and currently stands as an acceptable primary end point for regulatory approval by governmental agencies. This raises the question of how best to measure such a subjective symptom. In this review, we will describe the basis for dyspnea, provide a detailed description of the strengths and weaknesses of the current best tools used to measure it, and describe future directions for future development of dyspnea measurement in AHFS.