Some smooth muscle tissues exhibit a well- expressed spontaneous rhythmic activity which varies between different tissues. The role of the interstitial cells of Cajal (ICC) to generate spontaneous activity is still a matter of debate. Furthermore, it is unclear if excitatory signals propagate along the smooth muscle like in cardiac muscle via gap junctions. These problems can be solved with a three dimensional network analysis which demonstrates the coupling parameters under in vitro conditions. Spontaneously rhythmical active tissue was loaded with a calcium-sensitive dye (fluo-3. Using fast confocal microscopy, calcium signals were measured during time intervals of at least 3-5 activity periods. Cross correlation was calculated which gives the maximum similarity and the time lag between the two signals at two regions of interest. Coupling in longitudinal direction was nearly double the size in gastric antrum as in portal vein SM In transversal direction this property was comparable. Using a temporal resolution of 5 frames per second, no significant time lag was detected. It is concluded, that stronger synchronisation in antrum muscle is due to a better coupling between the smooth muscle cells and a larger synchronisation between the ICCs,.