A constitutive relation based on floe collisions as introduced by Shen et al. (1986) is used in a sea ice model for calculating the internal ice force. The formulation is generalized to collisions of discs of two sizes and of multiple sizes and a comparison with existing constitutive models is presented. A coupling of the floe collision model with a viscous-plastic model (Hibler, 1977) in the simulation of mesoscale sea ice processes in subpolar regions is suggested in order to account for the marginal ice zone dynamics. ¿ American Geophysical Union 1989