Objective: In Colorado, there has been a large increase in medical marijuana dispensaries and licenses for the use of medical marijuana over the past year. This is a retrospective case series of marijuana exposures that have presented to the emergency department (ED) in children less than 5 years of age. Methods: We performed a retrospective chart review of electronic health record from October 2009-March 2010 for patients less than 5 years of age with the ICD-9 code 969.6 (poisonings by psychodysleptics, hallucinogens) at a tertiary care, freestanding children's hospital. Results: A total of of five patients all less than five years of age who presented to the emergency department with symptoms of somnolence whose ultimate diagnosis was marijuana exposure. Four of the five home environments had the presence of medical marijuana cards. Conclusion: With the increasing use of marijuana for medical purposes and the expansion of marijuana into food products, exposures/ingestion in children are likely to increase in the future. Therefore, in medical marijuana jurisdictions, primary care and ED physicians should consider marijuana exposure/ingestion in the differential diagnosis of the child who presents with altered mental status, to enlist the services of a Child Protection Team where available, and to report such exposures/ingestion to the local child protective services. (Contains 1 table.)