Forty-one children, aged 1 to 5 years, who accidentally ingested levothyroxine sodium were studied. Symptoms possibly associated with the ingestion occurred in 11 patients (27%). These symptoms (tachycardia, hyperactive behavior, fever, vomiting, diarrhea, diaphoresis, and flushing) were categorized as minor and all resolved without treatment. Because observed effects were generally mild and often unrelated to either estimated amounts of hormone consumed or serum thyroxine levels, a conservative approach to patient treatment is recommended in cases of levothyroxine ingestion in children.