In most body imaging procedures, the effect of respiratory motion must be considered. For example, during deep inspiration the liver may move up to 75 mm caudally Weiss et al, 1972) and the CT attenuation value of lung tissue may change by over 100 Hounsfield units (Robinson & Kreel, 1979). Attempts have been made to “freeze” organ movement in radionuclide imaging by gating the detector with a physiological signal (Parkin & Unsworth, 1980; Smith et al, 1969). In conventional CT scanning, however, no gating is possible once the scan cycle has started and breath-holding techniques must be adopted. Although breath-holding may eliminate artefacts caused by respiratory motion, repeated scans at the same nominal slice position may show significant differences (Fig. 1), owing to inability to reproduce constant degrees of held inspiration or expiration. The following describes the construction and use of a respiration monitor with a “feedback” display for the patient, to aid breath-holding at consistent pre-selected levels. The equipment consists of a liquid column respiration transducer for measuring upper abdominal circumference, processing circuitry and light-emitting diode (LED) bar displays for the operator and patient.