Previous research has investigated the determinants and consequences of customer loyalty, but, in banking, a critical measure largely neglected in previous studies is the customer's ‘share of wallet’. This study, based on a survey of 1,924 retail banking customers, suggests that a large proportion of the variance in stated behavioural intentions can be predicted, in particular, by customers' attitude measures. More importantly, the study shows that a substantial amount of the variance in share of wallet can be predicted, allowing banks to identify and focus on customer segments where there is most potential for growth. In recognition of the fact that dissatisfied customers are a distinct segment, the study models actual behaviour in terms of share of wallet for dissatisfied customers. Implications for research and for business are discussed.