Abstract Organophosphorus compounds are known to cause toxicity, typically within a few hours following oral exposure, by inhibiting acetylcholinesterase. We report a case in which there was an initial absence of typical muscarinic symptoms, but the patient developed severe typical muscarinic symptoms more than 78 hours after oral ingestion of organophosphate. A 56-year-old male was brought to our hospital complaining of dizziness and nausea 13 hours after ingesting 250ml of 50% fenitrothion. Upon arrival, he exhibited nicotinic symptoms: fasciculations of his tongue and bilateral upper and lower extremities, without any signs of muscarinic symptoms. Because of sudden respiratory depression, he was intubated on the day of admission and received pralidoxime and activated charcoal. Forty-nine hours after admission, he was extubated, as his respiratory function had improved. However, he subsequently developed muscarinic symptoms, including diarrhea, miosis, and bronchorrhea and was therefore intubated again five days after the ingestion. Serum fenitrothion concentrations showed minimal decline between four and five days post-ingestion. Despite resolution of the initial nicotinic symptoms, this patient later developed severe muscarinic symptoms with minimal decrease in the serum fenitrothion concentration during the period. The redistribution from adipose tissue may contribute to the recurrence of the symptoms and delayed drug excretion in organophosphate poisoning.