Introduction and Aims: The current understanding is that the longitudinal muscle contraction begins before and outlasts circular muscle contraction during esophageal peristalsis in normal subjects. The goal of our study is to reassess the relationship between the contractility of two muscle layers using novel ways to look at the muscle contraction. Methods: We studied normal subjects using synchronized high frequency ultrasound imaging and manometry. Swallow induced peristalsis was recorded at 2 cm and 10 cm above the LES. Ultrasound images were analyzed for muscle cross sectional area and circularity index of the esophagus during various phases of esophageal contraction. A plot of the M-mode ultrasound image, muscle CSA and esophageal circularity index was developed to assess the temporal correlation between various parameters. Results: The muscle CSA wave begins before and lasts longer than the contraction pressure wave at both 2 and 10 cm above the LES. M-mode US images reveal that the onset of muscle CSA wave is temporally aligned with the onset of lumen collapse. The peak muscle CSA occurs in close proximity with the peak pressure wave. The esophagus starts to become more circular (decrease in circularity index) with the onset of muscle CSA wave. The circularity index and muscle CSA return to the baseline at approximately the same time. Conclusion: Onset of lumen collapse and return of circularity index of the esophagus are likely to be the true markers of the onset and end of circular muscle contraction. Circular and longitudinal muscle layers of the esophagus contract in a precise synchronous fashion during peristalsis in normal subjects.