Background: Better methods are needed for preterm labor diagnostication. We hypothesize 1) that depolarization of the myometrium propagates from fundus to isthmus, 2) that the propagation velocity (PV) is faster in labor than in non-labor, and 3) that PV can be determined by electromyography (EMG). PV may be the best EMG-predictor of preterm labor. Knowledge on how to determine PV is insufficient though. Objective: To investigate EMG-signals from laboring myometrium and to develop a method for determining PV. Method: We included 10 women in active labor. EMG-signals were obtained via three monopolar, abdominal surface electrodes placed vertically in the midline with a distance of 6.5-11.2 cm between the electrodes. Labview software was used for signal visualization and data processing. We calculated the PV from the distance between the electrodes and the time displacement of similar signals. For calculating time displacement, we used cross-correlation to identify similar signals. Results: Each contraction consisted of 25-45 fluctuations with variable amplitudes. Background fluctuations with smaller amplitudes were observed between contractions. The signal order was random and independent of the vertical electrode order. Conclusion: Depolarization of the laboring myometrium may therefore not occur in the direction from fundus to isthmus. Further investigation is needed for PV determination.