The cascaded transmission line theory of Paul and McKnight is used in this paper to predict near-end crosstalk (NEXT) and far-end crosstalk (FEXT) in a bundle of twisted wire pairs. The approach is validated using the CST Cable Studio commercial software and experimental data. NEXT and FEXT along twisted pair bundles are then evaluated using a pure deterministic approach for the electromagnetic coupling while taking into account the random distribution of victim and aggressor pairs in the bundle. The results obtained using the presented approach are compared with available simplified empirical expressions (ANSI/FSAN). It is shown that the simplified expressions are able to predict the overall trend of the power sum loss. However, they do not always provide the worst case values. The presented theory can find important applications in the design of data transmission systems for which accurate crosstalk modeling is a vital task. It can be used for example as a replacement for the experiments in obtaining the parameters of simplified models for NEXT and FEXT.