The current staging system by the National Pressure Ulcer Advisory Panel (NPUAP) classifies the stages of pressure ulcers (PUs) based on clinical assessment and visual inspection. We postulate that patients presenting with clinically superficial PUs (Stage I and Stage II) will have a greater depth of injury than predicted. On admission, patients with sacral PUs were staged according to the NPUAP classification system. Patients who were classified as having a Stage I or Stage II ulcer or suspected deep tissue injury were assessed with high-frequency (12-MHZ) ultrasonography (US) to identify any evidence of injury to the deep tissue. The study included 20 patients undergoing US for PUs of the sacrum. All patients, regardless of PU stage were found to have some evidence of deep tissue injury upon ultrasonographic examination. In patients with suspected deep tissue injury, we have found US to be a reliable diagnostic tool that confirms the clinical suspicion of deep tissue injury. PUs classified as superficial may have a component of deeper tissue damage.