"Stacker 3" is one of the most popular caffeine-containing weight-reduction supplements and it has ephedra-free properties as "Stacker 2 Ephedra-Free" in many countries, including Korea. We describe here a 26-year-old woman who took an acute intentional overdose of "Stacker 3"(approximately 50 capsules, total amount: 25 grams, as caffeine 250 mg/kg) and who had delirium, rhabdomyolysis and acute renal failure. She had to be treated by forced diuresis and urine alkalinization, and she subsequently recovered. This is the first such case report in the medical literature.