This part of ISO 15663 provides guidelines for the implementation of life-cycle costing for the development and operation of the facilities for drilling, production and pipeline transportation within the petroleum and natural gas industries. This part of ISO 15663 is applicable when making decisions on any option which has cost implications for more than one cost element or project phase. The process can be applied to a wide range of options, particularly when decisions are being considered on the following: — the process concept; — equipment location; — project execution strategies; — health, safety and environment; — system concept and sizing; — equipment type; — equipment configuration; — layout; — maintenance and logistic support strategies; — manning strategy; — manning levels; — operation strategies; — facility modifications; — spares and support strategy; — reuse and/or disposal. This part of ISO 15663 is applicable to all project decisions, but the extent of planning and management of the process will depend on the magnitude of the costs involved and the potential value that can be created. The guidelines will be of value when decisions are taken relating to new investments in projects or during normal operation to optimize revenue.