A prediction method for turbulent boundary layers in moderate to strong adverse pressure gradients is presented. The closure hypothesis for the method is the universal velocity defect law of Schofield and Perry (1972) which restricts the method to the prediction of layers in moderate to strong adverse pressure gradient. The method is tested against nine experimentally measured boundary layers. Predictions for velocity profile shape, boundary layer thicknesses and velocity scale ratio were generally in good agreement with the experimental measurements and were superior to those given by other prediction methods. Unlike other methods the present method also gives reasonably accurate predictions for the shear stress profile of a layer. The analysis presented here is compared with previous work and helps to resolve some disagreements discerned in the literature.