Aim: There is not much knowledge about the patterns of macroscopic electrical propagations in the wall of the urinary bladder. Recording from a large number of extracellular electrodes simultaneously is one technology that could be used to study the patterns of electrical propagations. Method: The urinary bladders from 6 guinea-pigs were isolated and placed in a Tyrode filled organ bath. A 16×4 electrode array was positioned at various sites on the serosal bladder surface and recordings were performed at different intravesical volumes. At the end of 4 experiments, carbachol (CCH; 10-6 M) was added to the superfusing fluid and electrical activities recorded. After the experiments, the extracellular signals were analysed and propagation maps constructed. Results: Propagation of electrical waves was detected in all experiments and at all sites on the bladder surface. Waves could originate from any site and propagate for a finite distance before terminating spontaneously. The vast majority of waves propagated preferentially in the axial direction and only a few propagated transversely. Increase in vesical volume decreased significantly conduction velocity (from 4.9±1.5 to 2.7±0.7 cm/sec; p< 0.05) whereas CCH did not have any major effect on patterns and speed of propagation Conclusions: Large electrical waves do propagate across the bladder wall, both in the dome, across the peritoneal reflection and in the base. The preferential propagation in the axial direction may have practical implications during surgical interventions. The electrical waves could form the basis for local spontaneous contractions in the bladder.