There is a growing interest in determining whether factors other than cognitive ability and previous academic performance can influence academic success in medical school (Ferguson, James, & Madeley, 2002). This is due to the limited number of places available on a medical degree and the focus upon personal qualities that are expected of medical students when they graduate and become practicing physicians (Powis, Bore, Munro, & Lumsden, 2005). There are a large numbers of potential characteristics that may be useful in medical school. However, few have attempted to reduce this number into more meaningful dimensions. In addition, the academic performance literature has focussed on the psychometric properties of assessments and largely overlooked the structure of academic performance. The aim is to combine the two divergent literatures and explore the dimensionality of medical student’s dispositional characteristics, and the underlying structure of medical school assessments. This is in order to determine whether dimensions of dispositional characteristics are predictive of different types of assessment. 181 medical students completed a battery of questionnaires during the first week of term in Year 1. Academic performance variables consisted of assessment undertaken by students during the first two years of medical school. Chapter 5 presents a Principal Components Analysis of assessments. Results suggest that there are three underlying dimensions in the data corresponding to Scientific Knowledge Assessment, Interpersonal Skills Assessment, and Practical Skills Assessment. The results are discussed in terms of current models of desired outcomes in education. Chatper 6 presents a Principal Components Analysis of dispositional characteristics in medical students. The results suggest that the 21 measured dispositions had three underlying dimensions corresponding to Emotionality, Intrinsic Motivation, and Interpersonal Traits. The results are discussed in terms of how the traits might theoretically combine in addition to the statistical combination of traits. Chapter 7 presents a series of five Hierarchical Linear Regressions to determine if the trait complexes identified in chapter 6 differentially predict performance on traditional measures of academic performance, and the three dimensions of performance identified in chapter six. Overall results suggest that previous academic performance and cognitive ability are consistent predictors of academic performance in medical school as such their continued use in selection procedures seems appropriate. Both GCSE and A-Levels differentially predicted types of performance. In addition, emotionality significantly predicted Year 1 performance and performance in practical skills assessment. This study therefore provided support for a three dimensional model of medical student academic performance. However the influence of trait complexes warrants further investigation later in a medical career.