The velocity field and hence stress field for two-dimensional large-amplitude folding of a viscous layer in a less viscous matrix has been determined theoretically by a series of linear incremental problems. The velocity field for each problem was found numerically using a modification of the finite element method. The model considered most representative of natural folds had the following properties: eta /eta 1 , (viscosity contrast)=42, L/h (wavelength/thickness)=12, A o (initial amplitude)=0.1h. Microstructures induced by intragranular flow of calcite and quartz have been used by many to determine principal stress orientations around natural folds of many styles and sizes, generally with similar results. Fabric data record cumulative intragranular flow during folding.