To calculate hepatic volume in the dog by single photon emission computerized tomography (SPECT), we determined the limits of the organ by choosing an isocontour on each section. This choice entailed prior calculation of an overestimated pseudovolume. The accuracy of the measurement in the animal then approached that of measurements in vitro. We used the method to monitor hepatic regeneration in the dog after 65% hepatectomy and detected oedema and postoperative trauma, and over a longer timespan, stagnation of regeneration and a secondary drop in hepatic volume.