Few educational studies have investigated how well information learned by medical students is retained over time. The primary aim of this study was to investigate how much of the paediatric core curriculum undergraduates remembered a year after originally passing their paediatrics examination. In addition, we looked at whether students' repeat performance is related to their approach to learning. Medical students were presented with 8 out of a possible 46 core curriculum short answer questions (Mark 1). A year later these same students were re-tested, without prior warning, on the same 8 questions (Mark 2) and a further 8 questions (Mark 3) from the bank of 46. The participants also completed the Revised two-factor Study Process Questionnaire to characterise their approach to learning. After a year, students scores had diminished by 51.2% (95% CI 48.2-54.2%, p < 0.0001) from a Mark 1 average of 89.1% (standard deviation, SD = 9.2%) to a Mark 2 average of 37.9% (SD 6.1%). Students who reported a superficial approach to learning achieved higher scores for mark 1 (4.1% increase (95 % CI 0.9-7.4%) per one standard deviation unit increase in Surface Approach score (p = 0.01). Neither deep nor surface approach to learning significantly predicted performance a year later (Marks 2 and 3). Students had forgotten more than half of the paediatric core curricular content that they had previously proven that they knew for their summative assessment. Adopting either a deep or superficial approach to learning did not predict ability to retain this information a year later.