This paper examines construction quality costs in Turkey. First, background information is presented on quality costing, on the prevention, appraisal, and failure (PAF) approach, and on PAF components. Secondly, a model is presented for determining the optimum level of total quality cost. Finally, a case study in which the costs of quality in a mass-housing project were collected and evaluated is presented. For the case study, the data were obtained in two stages: (i) during the construction period and (ii) after the delivery of residences. During the construction period, data were collected in collaboration with quantity surveyors and site engineers. During the delivery of residences, a questionnaire was administered to 655 householders, using face-to-face interviews. The importance of construction quality in a developing country was clarified by means of a cost-based analysis, in which the percentages of quality costs in the total cost to client were calculated separately, as was the optimum cost value of total quality. (c) 2004 Elsevier Ltd. All rights reserved.