Mitochondria play a central role in cell homeostasis. Amongst others, one of the important functions of mitochondria is to integrate its metabolic response with one of the major signaling pathways - the Ca(2+) signaling. Mitochondria are capable to sense the levels of cytosolic Ca(2+) and generate mitochondrial Ca(2+) responses. Specific mechanisms for both Ca(2+) uptake and Ca(2+) release exist in the mitochondrial membranes. In turn, the mitochondrial Ca(2+) signals are able to produce changes in the mitochondrial function and metabolism, which provide the required level of functional integration. This essay reviews briefly the current available information regarding the mitochondrial Ca(2+) transport systems and some of the functional consequences of mitochondrial Ca(2+) uptake.