Early in the management of acute illness, it is critically important that volume status is accurately estimated. If inappropriate therapy is given because of errors in volume assessment, acute mortality rates are increased. Unfortunately, as the gold standard of radioisotopic volume measurement is costly and time-consuming, in the acute care environment clinicians are forced to rely on less accurate measures. In this manuscript, the authors review the currently available techniques of volume assessment for patients presenting with acute illness. In addition to discussing the accuracy of the history, physical examination, and radiography, acoustic cardiography and bedside ultrasonography are presented.