Hemodynamic changes in the liver are induced by several agents and pathological conditions. Acute hemodynamic changes, vasoconstriction or vasodilation, caused by endocrine or paracrine signals, generally transient in nature, most frequently have regulatory purposes. They may provide adaptation of the liver to a new metabolic situation. Alternatively, they may also elicit specific responses in the liver in order to meet new necessities of the whole organism. Hemodynamic changes due to pathological conditions are generally much more stable and combined with long-term structural changes. The dynamics of both kinds of alterations can be investigated by means of pressure measurements or by analyzing the outflow profiles of indicator substances (indicator dilution technique). Such procedures have been used successfully during decades by many investigators. Both techniques can be combined in the resolution of a given problem. The present review has two main purposes: 1) to discuss the importance of the hemodynamic changes in the liver in health as well as in disease (especially portal hypertension); 2) to outline the advantages of the combined use of pressure measurements and indicator dilutions in the search of answers for a number of questions related to the hepatic microcirculation in different species, including humans.