In this study, the integrated routing problem is formulated as the mixed pickup-delivery asymmetric traveling salesman path problem (mixed-PDATSPP). It is noted that since return items are usually collected and brought back to a returns processing center that is different from the depot, we thus deal with a 'path-type' instead of a 'circuit-type' routing problem. It has been pointed out that the asymmetric traveling salesman path problem (ATSPP) is NP-hard (Chekuri and Pál, 2007). It follows that the mixed-PDATSPP is also NP-hard, as it generalizes the ATSPP arising when the set of pickup customers or delivery customers is empty. Therefore, the aims of this research are to first model the mixed-PDATSPP, and then propose an efficient and effective heuristic solution technique to the problem.