In this study, we aimed to develop a new method for detection of aspiration based on B-mode video ultrasonography and to evaluate its performance. To detect aspirated boluses by B-mode video ultrasonography in patients with dysphagia, we placed a linear array transducer above the thyroid cartilage and observed the area around the vocal folds. Forty-two ultrasonographic measurements were obtained from 17 patients with dysphagia who also underwent videofluoroscopy or videoendoscopy measurements at the same time. Aspirated boluses were observed in B-mode video ultrasonographic images as hyperechoic, long, narrow objects that passed through the vocal folds beneath the anterior wall of the trachea, with movement different from that of the surrounding structure. The sensitivity of aspiration detection was 0.64, and the specificity was 0.84. This newly developed detection method will enable patients with dysphagia to receive appropriate daily swallowing care.