BACKGROUND Vitamin D is essential for optimal bone health and muscle function. An alarmingly high rate of vitamin-D deficiency in the general population has been reported recently. The purpose of the present study was to characterize the extent of low serum levels of vitamin D among orthopaedic surgery patients. METHODS We performed a retrospective chart review of 723 patients who were scheduled for orthopaedic surgery between January 2007 and March 2008. Preoperative serum 25-hydroxyvitamin D (25[OH]D) levels were measured. The prevalence of normal (≥32 ng/mL), insufficient (<32 ng/mL), and deficient (<20 ng/mL) vitamin-D levels was determined. Logistic regression was used to assess risk factors for insufficient (<32 ng/mL) 25(OH)D levels. RESULTS Overall, 43% of all patients had insufficient serum vitamin-D levels, and, of these, 40% had deficient levels. Among the orthopaedic services, the highest rates of low serum vitamin-D levels were seen in the trauma and sports services, in which the rates of abnormal (insufficient and deficient) vitamin-D levels were 66% and 52%, respectively. The lowest rate of abnormal vitamin-D levels was seen in the metabolic bone disease service. Patients between the ages of fifty-one and seventy years were 35% less likely to have low vitamin-D levels than patients between the ages of eighteen and fifty years (p = 0.018). The prevalence of low vitamin-D levels was significantly higher in men (p = 0.006). Individuals with darker skin tones (blacks and Hispanics) were 5.5 times more likely to have low vitamin-D levels when compared with those with lighter skin tones (whites and Asians) (p < 0.001). CONCLUSIONS The prevalence of low serum levels of vitamin D among patients undergoing orthopaedic surgery is very common. Given the importance of vitamin D in musculoskeletal health, such low levels may negatively impact patient outcomes.