This book aims to assess the factors affecting on overhead costs of construction industry and the components of these costs in the Iraqi construction industry. Many references had reviewed to collect the factors that affect on the overhead costs and its items in a questionnaire. The mathematical and statistical methods used in analysis of the respondents' answers were performed. The significant factors and items were listed in a questionnaire as a pair-wise comparison matrix according to the fuzzy analytic hierarchy process (FAHP) technique scale. The algorithm of this technique was applied on the answers of experts to calculate the weights priorities. Formulas of equations were built from these weights to calculate the ratio of each effective factor, item of the project overhead costs (POH) and home office overhead costs (HOOH) items. It was tested the equation of main POH items through applying it on one of the executed projects as case study, then all of the equations were evaluated by reconnaissance of the expert opinions. They showed suitability for the application.