A substantial amount of research has in recent years investigated consumer satisfaction. One could argue that in a frequently used and standardised service such as public transport cumulative satisfaction is likely to be based on evaluations of several encounters with the service. Hence, a relationship should exist between encounter satisfaction and cumulative satisfaction. Only scarce empirical evidence supports however this causal hypothesis. This study focuses on critical incidents. A critical incident is an encounter that in some respects differs, negatively or positively, from what is expected. In several previous studies the frequency of critical incidents has been used as an indicator of overall cumulative satisfaction with a service. An aim of the present study is to examine if this is a valid practice.