Acetaminophen (AAP) overdose can result in potentially serious hepatotoxicity. The ingested dose and time from ingestion to presentation are important prognostic factors. Toxic dose in adult is thought to be at least 10 g or 200 mg/kg. However, early management of acute overdose should be guided by the plasma AAP concentration. The antidote for AAP poisoning is N-acetylcysteine (NAC). It provides complete protection against hepatotoxicity if given within 8 h of acute overdose. If the concentration is above the possible toxicity line as predicted by the Rumack-Matthew nomogram, either the 72-hr oral or the 20-hr intravenous NAC regimen should be administered. NAC is also effective if started late in patients with established hepatic failure. This article summarizes the current consensus of clinical assessment and management for acute AAP overdose.