Recent studies on quality management, certification, and supply chain management emphasize that (1) ISO 9000 certification is becoming a must for many companies to compete, and (2) quality is a strategic variable that should be considered and managed not only within the single firm, but also acrross the supply chain of which the firm is part. Nevertheless, many empirical works on ISO 9000 concentrate on the impact of certification on the impact of certification on companies' internal quality systems, whereas they do not pay the same attention to both upstream and downstream interactions across the supply chain, and to their influences on quality management practices and performance. This study examines whether the diffused adoption or knowledge/confidence in the ISO 9000 quality system requirements (i.e. `sensitivity' to certification) by diverse supply chain members can really influence quality management practices/procedures and operational performance of individual firms in supply chains. These topics are examined through analysis of data gathered by means of a survey based on a sample of 100 Italian certified manufacturing companies. It was found that those firms with the most advanced internal quality systems tend to by extensively from certified suppliers and to be reliant on the quality level of their deliveries. However, such trust on certified suppliers rarely implies the formalization of medium-long term cooperative programmes. As for performances, the impact of supply chain sensitiveness seems to be significant on punctuality, delivery speed and volume flexibility, while there are no significant effects on quality and cost performance