Structural analyses show that the Ailaoshan-Red River shear zone (ASRRSZ) in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ~58?56 Ma, at least from ~27 Ma to 22 Ma and at ~13?12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ~60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ~16?13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision. Structural analyzes show that the Ailaoshan-Red River shear zone (ASRRSZ) in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such conditions occurred the the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L-type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened befo re ~ 58 ~ 56 Ma, at least from ~ 27 Ma to 22 Ma and at ~ 13 ~ 12 Ma respectively. The first episode of slip in the ASRRSZ was to correspond to the initial collision of India and Asia at ~ 60 Ma. second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ~ 16? 13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left-lateral slip in the course of intracontinental convergence since the India-Asia collision.