Serum chromium is the preferred specimen type for evaluating metal ion release from metal-on-metal joint arthroplasty. Serum chromium levels may be increased in asymptomatic patients with metal-on-metal prosthetics and should be considered in the context of the overall clinical scenario. The form of chromium greatly influences distribution. Trivalent chromium resides in the plasma and is usually not of clinical importance. Hexavalent chromium is considered highly toxic; however, chromium serum levels should not be used to assess toxic exposures to hexavalent chromium as it is predominately taken up and retained by red blood cells. Symptoms associated with chromium toxicity vary based on route of exposure and dose, and may include dermatitis, impairment of pulmonary function, gastroenteritis, hepatic necrosis, bleeding, and acute tubular necrosis.