Research on reputation systems has mainly focused on the trust building function of reputation systems. The present research looks also at the trust rebuilding function of reputation systems, more specifically, the role of the short text comments given in reaction to a negative feedback. Online markets are noisy environments; rebuilding trust is therefore often necessary. This paper analyzes whether sellers´ reactions have the potential to re-build the trust between business partners. The central questions were: Do different types of trust violations have more or less detrimental effects on trust? Do reactions of sellers have any trust re-building effects? Which types of sellers' reactions are more effective in re-building trust? A distinction is made between morality-based and competence-based violation of trust and between two types of reactions that a seller can display, namely an apology or denial of the trust violation. Two online experiments among active eBay users in the Netherlands were conducted, using a random sample of members of a large Dutch commercial ‘opt in’ access panel. The advantages of this methodological approach will be discussed. The results show that the text comments accompanying negative feedback indeed influence trustworthiness judgments. Contrary to what has been reported in the literature, denial in case of morality-based violations of trust did not re-build trust. The implications for further research on re-building trust on the internet are discussed.