The generation and propagation of spontaneous activity in smooth muscle is still not fully understood. It is well accepted, that a special type of cells which are not contractile but electrically active can serve as pacemaker cells. These "Cajal-like cells" are interconnected with the smooth muscle cells which form a functional syncytium. Furthermore, these rhythm generators are believed to propagate the activity along the smooth muscle cells, comparable to the propagation of spike activity in a nerve fibre. The biological tissue properties can be measured by "Biological network analysis"– see Poster this conference. To what extend the coupling between the transversal located cells helps to synchronize the activity in longitudinal direction is however unclear. Smooth muscle preparations of gastric antrum and portal vein (both rat) were investigated in respect to their mechanical activity. A muscle flap (5x20 mm) was cut into two pieces, leaving the end (3 mm) connected to each other. This preparation was fixed at two mechano-electrical transducers (each trouser leg) and at a fixed point (trouser waistband) and contractile activity was continuously measured in vitro. The mechanical activity of such coupled preparation ("Rostocker Hose") was computed in respect of similarity and phase coupling between the two signals. Gastric antrum was coupled a magnitude stronger than portal vein smooth muscle. Changing the direction of the preparation did not show any preference of signal flow (aboral to oral or oral to aboral). Similar results were observed in portal vein. It is concludes, that signal generation and propagation in smooth muscle is more complex than that in nerve fibres and "Cajal like cells" must operate as distributed generators and "signal refreshers" being active in both directions.