The objective of this study was to evaluate the sensitivity to imazamox herbicide of 142 Italian weedy rice populations selected in a territory representing of about 90% of total Italian rice fields, on the basis of their phenotypic features (awnedness) and sampling location (north-west, south-west and east areas). Two experiments were conducted to assess the number of dead plants and shoot biomass reduction at different days after treatment (8, 15, 22, 29, 36, and 73 DAT) at the rate of 70 g ha-1. The experiments were carried out in greenhouse by seeding weedy rice in alveolar trays (3 seeds/alveolus) with 6 replications. Hierarchical clustering on the number of dead plants at different DAT resulted in five clusters of imazamox sensitivity. Cluster 4 contained 28 weedy rice populations, mainly awned (64%) which required longer time (48 days) to reach 80% control than the others. Cluster 3 was composed by 22 populations (68% awned) requiring shorter time (13 days) to obtain the same level of weed control. Clusters 1, 2 and 5 showed an intermediate behavior with 23, 32, and 30 days, respectively, in order to reach 80% control. Biomass reduction of the weedy rice treated with imazamox ranged between 66-93% compared to non-treated plants. Both the most (89% biomass reduction) and least sensitive (69% biomass reduction) groups of weedy rice populations were mainly awned. The results obtained from this study pointed out that Italian weedy rice populations gave a dissimilar reaction to imazamox herbicide.