First Clinical Results. Purpose: The significantly improved temporal and spatial resolution of Multidetector-Row CT opens up new possibilities for cardiac imaging. A method with retrospectively ECG-gated spiral acquisition is presented. Materials and Methods: A total of 10 patients underwent cardiac CT on a fast multi-slice CT system with 4 simultaneously acquired slices and 0.5 s rotation time (Siemens Somatom Volume Zoom). Continuous spiral data of the entire heart volume (5 studies precontrast for calcium scoring, 5 studies with contrast) were acquired together with the patient's ECG and reconstructed with dedicated spiral algorithms providing 250 ms temporal resolution. Three-dimensional image data sets were built up from overlapping slices that were reconstructed in an arbitrary, user-defined phase of the heart cycle (e.g., diastolic phase). To evaluate the capability of the method for functional imaging, complete image volumes were reconstructed from the same spiral data set in different phases of the heart cycle. Results: Within a single breath-hold, a spiral data set of the entire heart volume could be acquired. Typical scan times for standard examinations with 3-mm slice width were 12-17s, and for high-resolution CT angiographies of the coronary arteries with 1.25-mm slice width about 25-35s. Motion-free reconstruction of the heart and coronary arteries with high spatial resolution were possible in the diastolic phase of the heart cycle. Multiphase reconstructions from the same spiral scan data set were possible. Conclusions: Fast multi-slice spiral CT with retrospectively ECG-gated spiral reconstruction is well suited for three-dimensional and functional imaging of the heart, especially for high-resolution imaging of calcified coronary plaques and CT-angiography of the coronary arteries.