Highlights of nonlinear beam dynamics experiments at the Indiana University Cyclotron Facility (IUFC) cooler storage rings and their implications on the design and operation of storage rings are presented. Our experimental results during the period of 1992–1993 can be classified in the following categories: (1) determination of nonlinear betatron Hamiltonian near 1‐D resonances, linear coupling resonance, and 2‐D difference and sum resonances; (2) determination of synchrotron Hamiltonian in the presence of the rf phase and the rf voltage modulations; (3) synchro‐betatron coupling induced by dipole field modulation; (4) attractors of a weak dissipative Hamiltonian system; and (5) effects of tune modulation on particles trapped in resonance islands. Based on our experimental results, we have analyzed data of synchro‐betatron coupling resonances at the Large Electron‐Positron Collider at CERN. © 1995American Institute of Physics