Purpose -The purpose of this paper is to provide insights into the relationship between ISO 9001 conformance of suppliers and the quality of products they provide, within a procurement system of a manufacturer operating under contracts with the United States Department of Defense. Design/methodology/approach -Chi-square tests of independence were performed to compare the receipt acceptance rate of material provided by ISO 9001-conforming suppliers to that of non-ISO 9001-conforming suppliers, for more than 46,000 receipts representing twenty-one material commodity groups provided by almost 800 suppliers. Acceptance of receipts required conformance to both hardware and paperwork requirements. Tests were also performed on data subsets, to determine the impact of ISO 9001 conformance on product quality for each of twenty-one material commodity groups, for manufacturers versus distributors, and for two material control levels.Findings -For the overall data set, and for the majority of data subsets analyzed, the product quality of non-ISO 9001-conforming suppliers was significantly better than that of ISO 9001-conforming suppliers. When only hardware non-conformances were considered to cause rejections, the results were similar, but effect sizes were generally smaller.Research limitations/implications -The quantities of receipts and suppliers included in this investigation were very large; however, care should be exercised in generalizing the results, because of the potential influence of the defense industry-related requirements imposed upon the material and the suppliers. Originality/value -This is believed to be the first paper to investigate the impact of ISO 9001 conformance on product quality using a large quantity of actual product data, for both ISO 9001-conforming and non-ISO 9001conforming suppliers, in contrast to numerous assessments of quality impact performed using interview and survey data.Since the introduction of the ISO 9000 family of standards in 1987, there has been ongoing discussion regarding the impact of the standards on product quality. Two of ISO 9000's foundational predecessors were Mil-I-45208A, Inspection System Requirements, and Mil-Q-9858A, Quality Program Requirements, both issued in 1963 by the United States Department of Defense (DOD) to govern inspection and quality of military equipment and systems. The third primary predecessor of ISO 9000, and the one that it most closely resembled, was BS 5750, a British standard issued in 1979 that provided guidelines for quality management systems. The ISO 9000 family of standards has been accepted and adopted worldwide. As of the latest published ISO survey (ISO, 2009), more than 1,000,000 companies are registered to ISO 9000, representing 178 countries.The objective of the ISO 9000 series of standards was to define a set of requirements and practices that could be applied to organizations, regardless of the products or services they produce. Application of these practices, and conformance to the requirements, should enable an organization to ...