We simulate the behaviour of the Na+-Ca++ exchanger as a permanent regulator of Calcium homeostasis. As a consequence of an membrane potential or a concentration change, we numerically evaluate the participation of this exchanger in returning to equilibrium cellular conditions. In our model, the Na+-Ca++ exchanger is suppossed to work joined to other important regulation mechanisms such as the Calcium Pump, the Calcium Channels, the Calcium Buffers and, the passive Diffusion of Calcium, as described in past works. For evaluating the latter parameter, we are using a previously reported homogeneus multi-layer model of an spherical cell.The graphical and numerical results were obtained using a PC-based environment over the Matlab platform, and it was compared to the results obtained with a C-language simulation. The results showed the Na+-Ca++ exchanger is always participating in the transport of Calcium ions, and it only modifies its direction and/or its speed, as a consequence of a stimuli. Our model also simulate the reversible behaviour of the exchanger for free Sodium or Calcium variations, including the influence of the membrane potential and the affinity values.Because of the high time constant of the Na+-Ca++ exchanger, the simulation must be robust enough to evaluate all the changes ocurring during a long time. With our currently simulation programs, it is only possible to do it for the first seconds. Nevertheless, we are now working in the improvement (precision, speed, resources) of the work described, using a SGI workstation and a parallel processing environment.