Objective: To analyse the therapeutic effects and toxicity of the eponymous concoction described in Roald Dahl's book George's Marvellous Medicine. Design: Literature review. Setting: Two literature loving households in England. Participants: George Kranky and grandma Kranky. Main outcome measures: Clinical and toxic effects of the individual ingredients checked against those listed in ToxBase, the National Poisons Information Service's poisons database. Results: The medicine contained 34 ingredients. The most common toxic effect identified on ToxBase was nausea and vomiting (16 ingredients, 47%). Potentially life threatening effects were associated with 13 (38%) ingredients, including depression of the central nervous system, kidney injury, convulsions, cardiac toxicity, and mucosal erosion. The effects described in the book were accurate initially but then diverted from the most likely clinical outcome (death). Conclusions: Although Dahl ought to be applauded for his initial accuracy about the toxicology of the ingredients in George's marvellous medicine, the overall effect would be fatal catastrophic physiological collapse. Scientific exploration and experimentation should be encouraged in children, although any medicinal ingredients need to be checked for potential toxicity before being administered-to grandmas or anyone else.