Abstract: A method of analyzing timing uncertainty involves creating an accurate model of one or more circuit elements of a mesh circuit residing within a window that covers a subset of the mesh circuit. An approximate model of one or more circuit elements of the mesh circuit residing outside of the window is also created. Monte Carlo simulations are performed on the combination of the accurate model and the approximate model to determine a plurality of timing values, wherein each run of the Monte Carlo simulation varies one or more parameters potentially affecting the operation of the mesh circuit. An uncertainty associated with the circuit elements is determined, based at least in part on the plurality of timing values. One embodiment considers clock as the signal whose timing uncertainty can be determined. Other embodiments model and simulate the global drive circuit that drives the mesh circuit separately from the mesh circuit to take into account common path correlations in the drive circuit.