Objective American College of Chest Physician (ACCP) guidelines stratify deep venous thrombosis (DVT) risk in trauma patients based on injury pattern and pharmacologic prophylaxis. Screening is only recommended for patients with high-risk injuries who are unable to receive pharmacologic prophylaxis. However, the prevalence of lower extremity DVT (LEDVT) in trauma patients may be higher than reported in previous studies as many studies on DVT screening have not investigated calf vein DVTs (CVDVT) and have not exclusively targeted critically ill patients. Given that current ACCP guidelines recommend treatment of CVDVTs, we investigated the efficacy of duplex ultrasound (DUS) screening in critically ill trauma patients for all LEDVTs, including CVDVT, regardless of injury pattern, risk factors, or pharmacologic prophylaxis. Methods Medical records of 264 intensive care unit trauma patients who received DUS screening for LEDVT were retrospectively examined for the presence of injuries conferring high risk for LEDVT, patient specific DVT risk factors, and low molecular weight heparin (LMWH) prophylaxis. Results Forty (15.2%) patients had LEDVTs found on DUS screening, 24 (60%) were CVDVT, and 30% of all DVTs were diagnosed within 1 week of admission. Patients without high-risk injuries receiving LMWH had a 13.5% DVT rate, which did not differ significantly from the 19.7% DVT rate in high-risk injury patients not receiving LMWH ( P = .667). Conclusions Lower extremity DVT is common in critically ill trauma patients, particularly in the first week following injury, regardless of injury pattern, DVT risk factors, or pharmacologic prophylaxis. Previous studies have underestimated DVT rates by not investigating CVDVTs and not exclusively targeting critically ill patients. We recommend early and continued DUS DVT screening of all critically ill trauma patients.