Oilseed rape (Brassica napus) is an important source of oils for industrial and food processes. Agriculturally it is a useful break crop in cereal rotations but suffers from competition from broad-leaved weeds that can be difficult to control. To extend the range and efficacy of weed control options, herbicide-tolerant oilseed rape cultivars have been developed through both conventional and transgenic genetic modification processes. Here we compare the success of these approaches and discuss the implications of the new herbicide tolerance traits in agricultural production of oilseed rape. We conclude that the impact of HT traits on the agri-environment will be dependent on the nature of the trait and the management strategies under which it is employed. We find no evidence that the technology used in the production of HT cultivars has any influence on their performance as crops. In fact transgenic HT cultivars are simpler to monitor for agricultural and environmental impact than are conventional HT cultivars.