The purpose of this study are to investigate customers’ silence in case of service failure, the resultant behavioral responses, and the factors influencing silence. The previous research on service failure has discussed customers' complaints, efforts to recover, equity perception, and customer behaviors and aimed to understand company efforts to recover complaining customers and equity perceived by customers in these efforts and predict future customer behaviors. However, the situation in which most of the customers experiencing service failure become silent, instead of making a complaint, means that a company cannot have even a chance of such recovery. Silence is not simply absence of voice but has lots of meanings. Understanding these meanings may lead to an answer to the question of why customers keep silent and to the understanding of how the silence affects their behaviors. The fact that it is possible to recover from service failure through complaints, thereby making customers more loyal implies that it is very important to encourage customers not to become silent but to make a complaint. Nevertheless, most studies have focused on complaints, not on silence, in both practical and theoretical respects. Focusing on customers' silence, this study aimed to divide silence into several types according to its motives and analyze the effects of the silence on their behaviors. It also intended to examine the factors affecting customers' silence and identify the ones promoting silence. The purposes of this study are as follows: First, it aimed to classify silence types on the basis of the theoretical consideration of customers' silence. Silence was divided into positive and negative types: the former included prosocial silence and the latter included defensive and acquiescent silence. The motives and backgrounds of the silence and the characteristics of several types of silence were reviewed. This study can suggest that customers' silence could be caused by a diversity of motives and that the silence might be divided into various types according to these motives. Second, it aimed to discuss the factors that could reduce negative types of silence and increase positive ones. These factors were presented at the levels of companies and employees: companies' quality of complaint handling design at the former level and customer-employee tie strength at the latter level. An attempt was made to determine if these two factors could reduce the negative types of silence―defensive and acquiescent silence ―and increase prosocial silence. This study can make strategic suggestions concerning the measures companies might need to take to reduce negative types of silence. Third, it aimed to review the relationships between customers' silence and their behavioral responses. The switching intention and the word-of-mouth intention were suggested as customers' behavioral responses and an attempt was made to determine how each type of silence affected customers' behavioral responses. Another attempt was made to review the relative influence of the negative types of silence-defensive and acquiescent silence-on customer behavior. This study can determine what type of silence might more strongly encourage customers to do negative behaviors and serve as a greater determinant. This study obtained the following results: First, companies' quality of complaint handling design significantly affected customers' defensive and acquiescent silence. Quality of complaint handling design allowed customers to be less afraid of occurrence of negative situations, such as face loss and others' sharp look, which could accompany complaints, and to make unengaged thinking that expressing their opinions would be meaningless and that there would be little possibility of improvement. Therefore, high quality of complaint handling design encouraged customers to reveal the problems they experienced, thereby reducing the possibility of becoming silent. Second, customer-salesperson tie strength significantly affected prosocial silence. This is because the stronger customer-salesperson tie strength, the higher level of emotional intimacy between the customer and the salesperson and the greater possibility of the customer's considering and understanding the salesperson despite a bad situation. Accordingly, the customer may choose to become silent from an altruistic perspective. Third, customers' defensive silence significantly affected their negative word-of-mouth intention but had no significant effect on their switching intention. In contrast, customers' acquiescent silence significantly affected both their switching intention and negative word-of-mouth intention. Defensive silence is self-protective one, which may be chosen due to face loss, embarrassment, and blame but involve a desire to resolve their negative experience by telling it to someone. This is because they can be given comfort through conversation with members of a social network and have their wound cured. Fourth, as for the relative influence of defensive and acquiescent silence on customers' switching intention and negative word-of-mouth intention, the latter more strongly affected customers' switching intention and negative word-of-mouth intention than the former. This result implies that although both defensive silence and acquiescent silence are negative types of silence, the latter may more negatively affect customer behavior than the former. Fifth, prosocial silence had no significant effect on the switching intention but significantly affected the negative word-of-mouth intention. That is, prosocial silence reduced the negative word-of-mouth intention and caused them not to speak ill of the company or the employee to other customers. This is because prosocial silence is based on understanding and consideration in a tie and may cause them to think that negative word-of-mouth regarding the employee or the company is inappropriate for the established relationship. However, the finding that prosocial silence had no effect on the switching intention implies that although prosocial silence is positive one induced by positive motives, it cannot reduce all of the negative customer behaviors. These results suggest the need to take interest in the non-verbal expression, silence, as well as in verbal complaints in both theoretical and practical respects. In other words, it is important to review the reasons why customers choose to become silent despite failure and to take interest in the effects of the silence on customer behaviors as well as in how to cope with customers' complaints in case of service failure and recover from them. In this study, emphasis is placed on the fact that silence is not simply absence of voice but another strong message of customers, which has lots of meanings.