The role of the civil engineering estimator within the contractor's organisation has been well documented. Whilst this role and the estimators' tasks within the estimating and tendering process are well understood, little attention has been paid to estimators' expertise, how they make decisions at various stages within the tender period, the education and training needed to become an estimator and the psychological make-up of those whose work is fundamental to the survival and growth of the civil engineering contractor. Computer aided estimating systems have, for the last decade, been available to assist the work of the estimator. However, there remains debate concerning their contribution to the tasks of civil engineering estimators. The research incorporated: a detailed survey of the member companies of the Federation of Civil Engineering Contractors; semi-structured interviews of practising estimators; a study of career attributes by questionnaire and self assessment exercise; an empirical study of decision making based upon the technique of protocol analysis; and the development of a prototype expert system to assist estimators in the task of selecting subcontractors. The analysis of the estimators' decision making processes showed that 'expert, estimators operate within a hierarchy of goals and utilize mental checklists and templates to make decisions. Novice estimators repetitively collate information and then summarise on a general basis. Protocol analysis was demonstrated to be a suitable technique for studying the decision making processes of estimators. The technique was also found to make a significant contribution to the process of knowledge elicitation for expert system production. The study of estimators' past careers and experience established typical career profiles for the civil engineering estimator. These show both the formal education received and the practical experience gained before becoming an estimator. The attributes required by construction personnel wishing to take up a career in estimating were identified and a composite personality profile of the civil engineering estimator produced. The survey confirmed the importance of estimators' experience and expertise within the estimating and tendering process and showed that some 56% of the survey respondents currently used some form of computer aided estimating. The reasons for user dissatisfaction with current computer aided estimating systems were also identified. A prototype expert system developed to vet prospective subcontractors for construction work. This was shown to provide considerable assistance to estimators.