Colchicine for injection has been available in the United States since the 1950s. Although not approved by the Food and Drug Administration (FDA), intravenous (IV) cholchicine has been an accepted treatment for acute gout symptoms. Several additional IV uses have been studied, including treatment of familial Mediterranean fever, pericarditis, primary biliary cirrhosis, amyloidosis, and Behçet's syndrome. More recently, outpatient use of IV administration for chronic back pain has been advocated by alternative medicine providers but is not an accepted practice. Colchicine has well-known toxicities that limit its safe therapeutic use. IV doses that exceed the standard single-use therapeutic dose of 2--4 mg per episode of gout have resulted in life-threatening toxicity. In March 2007, two persons from Washington and Oregon died after receiving IV colchicine for back pain from an alternative medicine clinic in Oregon. This report describes the investigation, which determined that a measuring error by a Texas compounding pharmacy resulted in a fatal colchicine concentration that was eight times greater than the recognized standard level. A subsequent review of medical records revealed that a third death from colchicine toxicity in a patient treated at the Oregon clinic also occurred in March and likely was associated with the same compounding error. These deaths highlight the potential risk from use of IV colchicine for back pain and the possibly fatal consequences of measuring errors in compounding pharmacy products.