The purpose of this descriptive study was to evaluate feeding aspirations in adult patients receiving long-term mechanical ventilatory support, including the incidence of aspirations, the frequency of silent (clinically inapparent) aspirations, and differences between aspirators and nonaspirators. Aspiration data were determined by review of videofluoroscopic (VF) tapes of modified barium swallow procedures performed on 83 medically stable patients admitted to a chronic ventilator unit. Demographic and clinical variables were obtained from review of subjects' medical records. Forty-two subjects (50 percent) aspirated during VF testing and 37 of 48 (77 percent) aspirations were silent. Subjects who aspirated were significantly older than those who did not aspirate (p = 0.007). Swallowing disorders were common, particularly disturbances of the pharyngeal phase. We conclude that feeding aspiration is seen frequently in patients with tracheostomies receiving prolonged positive pressure mechanical ventilation. Advanced age increases the risk of aspiration in this population. Episodes of aspiration are not consistently accompanied by clinical symptoms of distress to alert the bedside observer to their occurrence.