Despite decades of study of stone decay phenomena and practical stone conservation experience, there are still great gaps in our knowledge, and it is still difficult to predict how stone decay and soiling will respond to changes in air pollution and other environmental changes. Nonlinear behavior and chaotic system dynamics have been recognized in many earth surface systems and are also relevant to stone decay phenomena. Identification of nonlinear behavior in stone decay systems should help interpret, model, and manage such systems. Several examples indicate the presence of nonlinear, and sometimes chaotic, behavior in stone decay systems. A review of sources of nonlinearity in stone decay systems illustrates that nonlinearities are common and important, with chaotic behavior sometimes resulting. Such findings illustrate the potential dangers of applying linear damage functions and the need for management efforts to take seriously nonlinearities in stone decay, due to the often complex and chaotic responses of deteriorating stonework to environmental changes.