The mutual dependence of various parameters--frame rate, radiation dose per frame, size of the image intensifier field, photon energy, frame mode, and patient diameter--is investigated systematically on a modern DSA equipment. The software programme of the DSA machine widely modifies these parameters according to the individual conditions, which may influence both radiation exposure and image quality. IV DSA requires low photon energies to exploit the low iodine signal. Higher frame rates, oblique views and small image intensifier fields should be used restrictively especially in the abdomen, as they tend to lower the radiation doses per frame and to increase photon energies, thus impairing contrast resolution. Full understanding of the physical and technical basics and familiarity with the software programme of own DSA machine are mandatory to allow appropriate selection of the various parameters, according to the individual patient and his/her diagnostic problems. They are the key to optimal imaging quality at a tolerable radiation exposure.