Many project managers feel the project network is their most valuable exercise and planning document. Project networks sequence and time-phase the project work, resources, and budgets. Work package tasks are used to develop activities for networks. Every project manager should feel comfortable working in an AON environment. The AON method uses nodes (boxes) for activities and arrows for dependencies. The forward and backward passes establish early and late times for activities. Although most project managers use computers to generate networks and activity times, they find a keen understanding of network development and the ability to compute activity times is invaluable in the field.Computers break down; input errors give false information; some decisions must be made without computer “what if” analysis. Project managers who are well acquainted with network development and AON methods and who are able to compute activity times will encounter fewer problems than project managers less well acquainted. Project networks help to ensure there are no surprises