The use of engineering consultants by state transportation agencies continues to be important in providing the appropriate solutions to transportation needs. This publication replaces the Guide for Contracting, Selecting and Managing Consultants in Preconstruction Engineering, published by AASHTO in 1996. In order to assess current practices, questionnaires were developed for both state and consultant practitioners. The responses showed significant growth in the volume of work done by consultants and in the range of services provided by consultants. The results of these surveys, along with the collective experience and expertise of the technical committee membership, were used to restructure much of the guide and to update and expand the discussion of current practices for the effective use of consultants.