Rigid ryegrass (Lolium rigidum Gaud.) is a weed that caused significant losses in yields. The results showed that the density of ryegrass varied depending with the climatic regions and increased with increasing of rain. However, the density of this weed increased to the lower semi-arid to the sub-humid climate regions. Maximum infestation (657 plants/m²) of ryegrass was recorded in sub-humid against 9 plants/m² in the lower semi-arid climatic regions. Study of the correlation showed that the yield losses were highly correlated with density (r = 0.92847 and p=0.0001) with an exponential equation y = 109,56 e-0,001x. The results of the field trials showed that pre-mix mesosulfuron-methyl 7.5 g/ha + iodosulfuron-methyl-sodium 7.5 g/ha, pyroxsulam 23.3 g/ha and fenoxaprop-p-ethyl 64 g/ha + iodosulfuron-methyl-sodium 8 g/ha and chlortoluron 2400 g/ha controlled ryegrass effectively. At some locations, herbicides ACCase inhibitors (pinoxaden at 45 g/ha, diclofop-méthyl at 625 g/ha + fénoxapropo-p-ethyl at 50 g/ha and tralkoxydim at 320 g/ha) and ALS inhibitors (sulfosulfuron75% at 26.6 g/ha and flucarbazone sodium 70% at 43 g/ha) showed poor efficacy which may be due to the development of resistance in rigid ryegrass in many locations of Tunisia.