Background Among the general population, accurate knowledge of child development is poor. Residents and staff physicians in family medicine and pediatrics have identified significant gaps in their knowledge or training in this area. Objectives To assess medical students baseline knowledge of child development Methods 103 first year medical students (61% response rate) were recruited from the University of Alberta prior to any formal instruction in child development. They completed an online questionnaire that included demographic items as well as 17 questions on the age at which most children attain certain developmental milestones. The questionnaire had previously been administered to a general population sample. The students performance was compared to that of the general population. Results The average student answered 24% of questions on developmental milestones correctly. Knowledge of non-motor milestones was significantly worse than knowledge of motor milestones (p<0.001). No demographic factors predicted greater knowledge of developmental milestones among medical students. Medical students performed significantly worse than a sample of adults drawn from the general population, both overall (p<0.05) and specifically on questions testing motor milestones (p<0.05). There was no significant difference between the two groups on questions testing non-motor milestones. Conclusions At the start of their training, medical students lack basic knowledge of child development. Their knowledge of the less visible developmental sectors is especially poor.