The study has various distinctive features. Previously there has been no meaningful research on the relationship between personality traits and consumer behaviour variables. Most previous studies were directed towards establishing a relationship between individual personality traits and buying behaviour or to predict sales of expensive items such as automobiles, in which personality was not the only influencing factor. Moreover, almost all of the earlier work on personality traits and consumer decision-making, was targeted at the study of products not services. In contrast, the current study was aimed at ‘usage’ behaviour rather than ‘buying’ behaviour; and building the conceptual framework on services rather than products. Using two studies [(N=987 for Mobile Phone Services) & (N=288 for Credit Card Services)], consistent support was found for the effects of personality traits on customer loyalty, satisfaction and switching patterns among mobile phone and credit card users.