The evolution of herbicide resistance in weeds is a worldwide phenomenon in modern cropping systems. The presence of resistant populations can severely hamper herbicide-based weed control, thus leading to the need for a more accurate use of these products. In Tunisia, the first report of evolved herbicide resistance concerned Lolium rigidum populations collected in wheat fields in northern Tunisia in 1996 and found to be resistant to acetyl-coenzyme A carboxylase-inhibiting (ACCase) herbicides. The objective of this study is to detect and characterise herbicide resistance in ryegrass (Lolium spp). The sensitivity of nine ryegrass populations, collected in wheat fields in northern Tunisia, was performed with two ACCase-inhibiting herbicides and an acetolactate synthase (ALS)-inhibiting herbicide. Resistant plants were genotyped to detect mutant resistant ACCase and ALS alleles. The results showed that resistance to clodinafop is very developed, as it was observed in all populations tested. However, resistance to sulfonylurea is less developed but seems to be emerging. Although the mutant ALS resistant alleles account for most of the resistance to sulfonylurea, those of ACCase explain less than 20% of the resistance observed in ryegrass populations. The other part would be due to other mechanisms that are likely metabolism-based resistance. The cross-resistance pattern conferred by this type of resistance is very unpredictable as it may relate to different herbicide chemical families and this could explain the resistance observed in some populations for the new molecule pinoxaden. To reduce the spread of the phenomenon of resistance in wheat fields, chemical weed control could not by itself be a long term solution. The use of integrated crop management methods, including cultivation and the alternation of different herbicides and modes of action, would be proposed.