This study sought to determine the magnitude and direction of achievement gender differentials at the UWI medical school in St. Augustine. This tertiary institution provides a unique opportunity to investigate gender differentials in the English-speaking Caribbean because males and females are self-selected and equally matched in ability. The study is set in the context of a variety of innovative teaching-learning strategies, assessment modes, and disciplines throughout an extended 5-year programme. Data for 9 years (graduating class 1994 to 2002) were collated and analyzed. The size and direction of differentials were evaluated using Cohen's D and Eta-squared. Additionally, the Standard Deviation Ratio (SDR) was used to compare variability in score distributions. The findings suggest that males had a slight advantage in the pre-clinical assessments whereasfemales did better on most clinical assessments. However, overall, not many differentials were medium or large-sized (Cohen's D >0.5). It was apparent that differentials were influenced by both assessment mode and discipline, withfemales performing better on constructed response and performance assessments in the clinical disciplines and males doing better on selected response assessments and the pre-clinical disciplines. It is recommended that institutions in the English-speaking Caribbean evaluate the impact of assessment mode upon gender differentials and work towards developing gender fair assessment schemes.