Optimal design methods that use continuum mechanics model for the deformation of the elastic body, are capable of generating suitable topology, shape, and dimensions of compliant mechanisms for desired specifications. Elastic analysis with linear finite element models employed in the synthesis procedures to date is not quantitatively accurate for large displacement situations. Also, the design specifications involving nonlinear force-deflection characteristics and generation of a curved path for the output port are difficult to realize with linear models. In this paper, the synthesis of compliant mechanisms is performed using geometrically nonlinear finite element models that appropriately account for large displacements. Frame elements are chosen for developing the synthesis procedure because of ease of implementation of the general approach and their ability to capture bending deformations. A computationally efficient method for computing the nonlinear design sensitivities is described. Examples are included to illustrate the usefulness of the synthesis method.