This research set out to answer the question, Should we abandon Type A in favour of the Big Five model? In order to do this, two dilemmas still being raised in the Type A literature also need to be answered. Firstly, is the global definition of Type A sufficient to describe Type A personality, or do we need to look at the factors of Type A? Secondly, is the Big Five 'big enough' to describe all personality theories including Type A personality? Before we could answer these, an extensive reVIew of the Type A personality literature, the Big Five and social desirability was conducted and two pilot studies were designed to eliminate as far as possible the impact of socially desirable responding. Two research studies were conducted. One was designed to examine the factor analytic structure of Type A to see whether the Big Five, according to correlation and multiple regression evidence, could explain Type A. The second· examined the relationships between the Type A factors, work performance and negative affect and looked at whether the factor model of Type A has incremental validity over and above two global Type A models and the Big Five. This research found several advantages in using the Type A factor model over the global Type A model, and. found that the factors added incremental validity in the prediction of negative affect and work performance. This suggests that the global definition of Type A is not enough to describe Type A personality. The research also found that the Big Five underlie most, if not all, theories of personality including Type A although it does not predict negative affect better than Type A. The Big Five may not therefore be 'big enough' to describe Type A personality and is not the answer to the 'Type A personality problem'. On the basis of these findings, therefore, this research establishes that Type A should not be abandoned in favour of the Big Five but instead highlights that both make important contributions to defining Type A. Recommendations for further work in this area are proposed.