Diversity in environment and socio-economic conditions characterizes the cotton-based cropping systems found in South-East Asia. However, beyond these differences, all systems are facing two major constraints : (i) a severe and persistent pest pressure which limits yield and drives almost all the changes and performances of the systems (ii) a competition with other upland crops (field or horticultural crops) accentuated by new opportunities offered to farmers as the result of a deeper integration of upland agriculture into the market economy. These constraints vary in intensity with the cropping techniques and cropping patterns adopted by fanners, but also according to the level of integration of agriculture to market economy together with the agricultural policy of the country. This paper presents key issues of a comparative approach of some cotton cropping systems of Thailand, Vietnam and Laos which display contrasted cropping techniques and correspond to different stages in market integration of the farming systems. During the transformation process of upland agriculture, cotton is a key cash crop in the transition to market-oriented farming systems. Because this transition first started in Thailand some 30-35 years ago, the Thai experience is particularly useful to neighboring countries. In this country cotton was an important crop for capital accumulation on small-scale upland farms. At present cotton producing farming systems are in small number and are much diversified. Changes in the cotton systems observed in the three countries exemplified the concept of subsistence/exploitation/ crisis pattern in cropping systems in relation to pest control. However cropping systems in Thailand and Vietnam displayed contrasted strategies of response to pest constraints. Moreover, competitiveness of cotton in comparison to other upland crops is eroding because of low improvement in productivity and high risks of failure of the crop. The sustainability of cotton-based cropp