Variety assessment could be supported by the use of dynamic crop modelling. The SUNFLO model was developed to simulate the achene yield and oil concentration of sunflower crop with a special attention paid to the description of varietal diversity. For that purpose, a variety was characterized in the model by 12 parameters of phenology, leaf area development, allocation and response to water stress. These parameters were measured either in field conditions (dense stands) or in greenhouse pot experiments. In 2008, two variety trials were carried out by CETIOM in non limiting conditions and a greenhouse experiment was conducted by INRA to calibrate the response of leaf expansion and plant transpiration to soil water depletion. The model parameterized with these 3 experiments on 18 commercial varieties was evaluated for yield in 42 situations of the post-registration network conducted by CETIOM in France in 2008. The yield of a given variety in a given environment was simulated with a mean error of 5 q/ha (relative error = 16%). When averaging a variety over all the environments or an environment over all the varieties, the error was of 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