It is claimed that, nationally, women undergraduates obtain proportionately fewer First Class degrees than their male counterparts. This thesis examines the extent to which gender differentiation in First Class achievement exists in Higher Education. Historically, various hypotheses have been presented within literature on Higher Education to account for this pattern and the thesis explores the extent to which these hypotheses continue to hold explanatory power using the University of Sussex as a case study. To ascertain the hypotheses' continued relevance and salience, a multi-faceted methodological approach was employed. The empirical programme comprised a national (N=657534) and a local statistical survey (N=8349) examining HESA defined subject groups, in addition to a local statistical survey (N=568) examining specific disciplines. The empirical programme also included detailed analyses of a student cohort of 'high achievers' (N=199) who were tracked throughout their degree. A range of information was collected on this cohort including cognitive ability and personality test scores, socio-demographic data, pre-university qualifications and measures of application. Some of the cohort (N=84) completed a questionnaire, and interviews were carried out with a smaller sub-section (N=23). Structured observations of seminars (N=24) were also conducted alongside interviews with members of faculty (N=21). Findings indicate that, nationally, gender inequity in First Class performance is prevalent in the Humanities, Social Sciences and Physical Sciences. In relation to local patterns of performance, evidence suggests that the University of Sussex may be spearheading incipient shifts in attainment with gender differentiation in existence only in the Humanities. Notwithstanding this moving and improving picture vis a vis the gender distribution of Firsts, the thesis concludes that many of the hypotheses remain pertinent.