The bid mark-up estimation is an unstructured decision problem that is usually solved by intuition. The aim of this paper is to present a decision support tool so that bid mark-up values may be estimated in a more systematic way. For this purpose, various factors that may affect the level of risk, opportunity and competition in a project option have been identified. Using the 95 cases obtained from the Turkish contractors working in international markets, a case-based reasoning model (CBR) has been developed to estimate the risk, opportunity and competition ratings. These ratings are further converted to risk and profit mark-up values by using linear utility functions constructed according to the boundary values which were identified by the respondents considering worst, average and best scenarios. The applicability of the model has been demonstrated on a real case study. (C) 2007 Elsevier B.V. All rights reserved.