Anesthetized dogs were scanned in the dynamic spatial reconstructor, a fast multislice computed tomographic scanner. In one group of eight dogs, four differently radiolabeled microspheres (1.5 mum diameter) were injected into the left atrium, with each label corresponding to a different hemodynamic condition. The image data collected from this group of dogs were used to develop the algorithm for estimating regional myocardial perfusion from the CT image data. In an additional 11 dogs, three differently labeled microspheres were also injected during different hemodynamic conditions. The image data collected from this second group of dogs were used to prospectively evaluate the accuracy of the algorithm developed from data in the first group of dogs. The results are presented and discussed.