Dextromethorphan (DXM) is a common component of combination cold medications that has become a popular drug of abuse for young adults. Abusers of DXM have developed a simple acid-base extraction technique to "free-base," or extract, the DXM from the unwanted guaifenesin, coloring agents, sweeteners, and alcohol that are typically included in combination cold preparations. We report a case of DXM overdose after ingestion of this purified "Crystal Dex" and discuss the "Agent Lemon" and single-phase extraction techniques that are used to free-base the dextromethorphan.