In recent times, biotechnology has been widely used for crop improvement. Today, about 2 billion hectares of global area is planted with genetically modified (GM) crops. In India, the first GM crop to be introduced was Bt cotton. The current acreage planted with Bt cotton is 93% of the total cotton acreage. However, the average yield is lower than that of other countries suggesting an opportunity to increase yield further. One of the major factors affecting yield is weed competition which reduces yield by 50 to 85%. Effective weed control is achieved by Integrated Weed Management (IWM) which includes adoption of transgenic herbicide tolerant crops (HTCs). The major transgenic HTCs grown in the world are soybean, cotton, corn and canola and the yield increase due to effective weed management is significant. In cotton, glyphosate and glufosinate tolerant systems have been used successfully across the globe and are being tested at the moment in India. Over reliance on single MOA (mode of action) rather than a diversified IWM system with multiple, complementary herbicide MOAs can lead to emergence of herbicide tolerant weeds. Therefore, there is a need to use diversified management practices for sustainable weed control in cotton.