Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2008.3423.3430GhoddosiP. P. JalalM. HosseinalipourM. 122008819On-time completion and conformity with assigned costs of every project or plan is one of the most important factors in success of that project or plan. No completion or overrun cost leads to not meeting the employer`s requirements need or goals of the plan or the project. This issue is of greater importance in large and national projects in which the period of execution is long even in normal conditions and takes more than 6 years averagely. Dam construction projects are of especial importance regarding on-time completion and assigned funds because of their importance in operation size, great investment, complicated nature and many uncertainties in them like underground conditions, natural disasters and high cost of construction. So, inspection, identification and evaluation of causes of cost and time overrun and representations of solutions for obviating them have great benefits for economy of the country. Besides in most cases precise and sufficient information is not available for this purpose and opinions of experts and professionals in this project (in fuzzy theory framework) should be used. In this study, in addition to brief review of studies related to the issue of delays, fuzzy theory and method of using it is explained and real value of cost and time overrun in some dams of Iran is calculated and subsequently, fuzzy identification and evaluation of causes and cost and time overrun in these projects are dealt with.]]>Anandalingam, G. and M. Westfall,1988186985Al-Moumani, H.A.,2000185159Arditi, D. and M.A. Robinson,1995372028Arditi, D. and B.K. Patel,1989115144157Abdulaziz, A.B. and M.J. Cunningham,1998124245341Odeh, A.M. and H.T. Battaineh,2002206773Ahmed, S.M., S. Azhar, P. Kappagntula and D. Gollapudil,20032003pp: 257266Alaghbari, W.A.M.,20052005Al-Khalil, M.I. and M.A. Al-Ghafly,199917101106Flyvbjerg, B., M.K.S. Holm and S.L. Buhl 1995237188Bogardi, I. and A. Bardossy,19831913941402Chen, S.H.,198517113129Frimpong, Y., J. Oluwoye and L. Crawford,200321321326Klir, G.J. and T.A. Folger,19881st Edn.Michael, R.F.,199912596100Office of Government Commerce,19951995Pillai, N.V. and K.P. Kannan,20012001Peter, W.G.M. and G.H. Hough,19871st Edn.Kartam, S.,1999125409419Stumpf,2000423243Schumacher, L.,1995371113Sadi, A.A., M. Al-Khalil and M. Al-Hazmi,1995114550Morris, S., 199025M154M168Terry, W.,2003211926The Report of the World Commission on Dams (WCD),20002000Wang, L.X.,19971st Edn.,Pages: 424Pages: 424Zadeh, L.A.,19658338353Said, B.,20052005pp: 132