Herbicide tolerant (HT) canola (Brassica napus L.) varieties were selected from spontaneous (triazine) or induced mutation (sulfonylurea) and through gene transfer technology (glufosinate, glyphosate). Since 1995, these varieties have been drastically developed in North America and more recently in Australia. Agronomic and economical genetic benefits of herbicide tolerance were monitored in field conditions in these countries. Before developing this strategy in Europe, there is a need to estimate potential benefits and undesirable impacts of HT varieties in our specific conditions. Main constraints expected from HT varieties are due to gene flow in or outside cultivated fields from rapeseed volunteers as well as from seed and pollen dispersal, and to potential outcrossing with related species B. rapa, wild radish, hoary mustard and wild mustard). Field experiments have been carried out in natural conditions by academic research in connection with professional organizations to develop and to validate gene flow models useful in various conditions. Long term studies need to be focused on large scale field experiments, long distance pollen dispersal in discontinuous designs and on the evolution of spontaneous populations and interspecific hybrids.