Aspiration is defined as the inhalation of oropharyngeal or gastric contents into the lower respiratory tract, or the situation that substances from the outside environment are accidentally inhaled into the lungs. The elderly individuals are at high risk of aspiration, while asphyxiation and pneumonia caused by aspiration are two most common causes of death among the elderly. Aspiration can be clinically classified as dominant and occult. The dominant aspiration can be easily diagnosed based on typical clinical symptoms, while there is a high rate of missed diagnosis on occult aspiration because of its hidden clinical manifestation. In this paper, we summarized various diagnostic methods for aspiration, especially the occult aspiration in the elderly.