Chromium is a naturally occurring, toxic heavy metal used in many industrial processes. The U.S. Department of Labor's Occupational Safety and Health Administration has established specific limits for occupational exposure levels of chromium and guidelines for medical surveillance of individuals who have been exposed to chromium. The author presents a case in which a 54-year-old man who had been working with chromium exhibited persistent elevations of urinary chromium levels after the cessation of occupational exposure. The author determined that the elevated chromium levels were caused by the patient's knee prostheses, which were made of cobalt-chromium alloy. The author also discusses mandates and screening guidelines for occupational chromium exposure and reviews the literature on chromium levels in individuals with prosthetic joint implants.