Stiffness reduction in [S,90n]s symmetric laminates, containing orthotropic sub-laminates (S) is analyzed as a function of crack density in 900 layer. Closed form expressions relating stiffness changes to the transverse crack density are used to compute stiffness changes due to accumulated damage. Weibull strength distribution of 900 layer is assumed and Shear Lag and Hashin’s models are used for calculation of stress distribution in 900 layer with cracks. Weibull parameters are obtained from experimental data for [02, 904]s laminate and then used for other lay-ups. Strength approach and Monte-Carlo simulation is used to estimate damage evolution in 900 layer and crack density as a function of applied strain is obtained. It is used to predict stiffness changes in [S,90n]s laminates as a function of applied strain. Predictions are compared with experimental data for [±θ, 904]s θ= 0,15,30,40 GF/EP laminates. Comparison shows fairly good agreement between prediction and experimental.