The problem under investigation is the failure of current project cost control processes in Australia to adequately examine alternative design solutions due primarily to the imposition of time and cost constraints. Hence project optimisation does not occur-- the cost of a design is controlled but rarely is a design formulated to comply with a pre - determined budget allocation . This thesis attempts to improve current practice through the introduction of a computer guidance system called "COSTPLANNER!" devised to enable implementation of complex optimisation and control procedures between the stages of conception and tender while simultaneously improving speed and accuracy. In order to arrive at a workable solution the investigative study is subdivided into three main sections. First, traditional methods of project cost control are discussed in order to ascertain the basic philosophies which will need to be preserved. Second, current levels of computer involvement are analysed to arrive at the essential elements which any computer - based system must possess. Third, a framework for a complete computer- guided cost planning package, incorporating the necessary mechanisms to enable more thorough investigation and overcome restrictions curre.ntly imposed by insufficient time, is designed in detail. The investigation has highlighted that design optimisation must be initiated at an early stage before valuable time and money is spent documenting a Bcheme that is inherently cost expensive . Also, to enable proper exploration of alternative solutions either the number of areas to be investigated must be r educed or the speed with which such area s are examined increased . The use of computers to undertake cost control activities means that the latter is an achievable goal that does not resist acknowledged attempts by the National Public Works Conference (N .P.W.C. ) in Australia to encourage industry standardisation. The major conclusion reached is that current practice can be significantly improved through the utilisation of computer guidance systems at all stages in the design of a project . Preparation time of feasibility reports can be reduced by ninety-three percent, sketch design cost plans by forty-five percent and tender document cost plans by thirty-four percent an overall reduction in time and cost of fifty percent. In addition to the obvious benefits of making instantaneous changes to cost information, full reports including life cycle costing, value analysis and cost- benefit analysis studies as applicable are automatically prepared . Implementation of computer guidance systems to improve efficiency is not only desirable but absolutely essential, although it is an area which t o date has been suprisingly ignored.