The uterine electromechanical activity was studied in 12 mongrel bitches. The uterus was exposed under general anesthesia, and 2 electrodes were sutured to its serosa. The electric activity was recorded for 30 minutes/day for 10 days. Simultaneous electric and mechanical activity (registered by a 4 F catheter connected to a pressure transducer) was also studied without and with uterine distension by a balloon. The electric activity was further recorded after performing uterine annular myotomy proximal and distal to the electrodes and between them. Pacesetter potentials (PPs) were registered from the 2 electrodes, having identical frequency and regular rhythm by the 2 electrodes, and were consistent in the individual dog on all test days. Action potentials (APs) followed PPs randomly and were associated with increase in uterine pressure. Balloon distension of the uterus effected increased PP and AP frequency. Annular uterine myotomy led to PP and AP disappearance distally but not proximally to myotomy. In conclusion, the study demonstrates that the uterus possesses electric activity represented by PPs which spread caudally. APs seem to be contractile waves. Recording of the electromecha­nical activity of the uterus may be of diagnostic significance in uterine disorders.