ABSTRACT: Context: The theory that there is a possible correlation between blood types and personality characteristics has been floating for a long time. Though there have been many attempts to evaluate this theory, the results have been inconsistent and can be best described as conflicting. Aim: The aim of our study was to explore a possible correlation between blood groups and certain specific personality traits, in a large sample of medical students in south India.Setting: The study was conducted at Karpaga Vinayaga Institute of Medical Sciences, Maduranthagam, India, in November-December, 2012.Participants: Our study included 502 medical students of the age group 18 – 22 years.Methods: ABO blood typing was done using the Agglutination method. For assessment of personality traits, we used one of the most researched, reliable and validated personality assessment tools, namely the Eysenk Personality Questionnaire – Revised (EPQ-R). EPQ-R assesses the three major personality dimensions: P (Psychoticism or “Tough Mindedness”), N (Neuroticism or “Emotionality”) and E (Extraversion or “Sociability”). Analysis of data was done using SPSS software (version 15). MANOVA and Tukey’s HSD were the statistical tests used to determine statistical significance. Results and Conclusion: Our study revealed a significant difference in ‘Extraversion’ scores between the blood groups B and AB. However, when the analysis was done separately for males and females, there was no significant correlation between blood types and personality traits. This implies gender was probably a confounding factor responsible for the initial difference in ‘Extraversion’ scores. So, the conclusion of our study was that there was no real correlation between blood groups and personality traits.