Variety assessment could be supported by the use of dynamic crop modelling. The SUNFLO model was developed to simulate the grain yield and oil concentration of sunflower crop with a special attention paid to the description of cultivar diversity. For that purpose, a cultivar was characterized in the model by 12 parameters of phenology, leaf area development, allocation, oil production and response to water stress. These parameters were measured either in field conditions (dense stands) or in greenhouse pot experiments. The model was parameterized on 18 cultivars and evaluated for yield in 33 situations of the post-registration network conducted by CETIOM in France in 2008. The average gap between observed and simulated grain yield was 3.5 q/ha (relative error = 11 %). The model could be used to rank environments (through sunflower crop response) in a variety assessment network and to separate varieties with sufficient phenotypic differences.