Objective To study the circumferential stress strain properties of layered esophagus in vitro.Methods A total of 8 male Wister rats were anesthetized and the esophagus were marked on the surface in vivo, excised and placed into the calcium free Krebs solution with dextran and EGTA added. The middle parts of the esophagi were selected for distention test and were separated into inner (mucosa and submucosa) and outer (muscle) esophagi. In distention tests the intact and layered esophagi were elongated to the in vivo length respectively with the pressures were applied in a ramp way at the rate of 2 cm H 2O per minute. The stresses and strains were computed from the morphometric data obtained from the images using the definitions by Kirchhoff and Green. Zero stress state was used as the initial reference for the stress strain analysis. Results The esophagus shortened axially by 24% after excision. The circumferential stress strain curves in intact and layered esophagus fitted well to mono-exponential function: τ=(τ *+β)e α(ε-ε *) -β(determination coefficients >0.96). Comparing the stress strain curves of intact esophagus, the curves of inner esophagus were shifted to the left ( P<0.05 ); and the curves of outer esophagus were shifted to the right (P >0.05). The differences between the curves of the inner and outer esophagus were also significant (P <0.05).Conclusion The circumferential stress-strain properties of the intact and layered esophagus showed non linearity. The inner esophagus is stiffer than the outer and intact esophagus.