Aspiration pneumonia is a major cause of death in the elderly. In this study, a water swallowing test was introduced as a method of evaluating the swallowing ability of patients, and a swallowing ability evaluation team investigated an appropriate procedure and evaluation method for the situation of our hospital. We also investigated the relationship between the swallowing ability of patients examined by the water swallowing test and underlying diseases, complications, and medicated drugs. In the water swallowing test, the water-drinking method was fixed, and evaluation was made based on the time required for drinking, profile, and episodes, by which patients suspected of swallowing disorder were detected, confirming the usefulness of this method. The frequency of developing swallowing disorder was significantly higher in patients with cerebrovascular disorders, Parkinson's syndrome (p<0.01, respectively) and symptomatic epilepsy, hypertension (p<0.05, respectively) as underlying disease/complication. Regarding medicated drugs, H₂ blockers were related to swallowing disorder (p<0.05). It was confirmed that patients who were judged as having swallowing disorder (including suspected cases) by the water swallowing test, and patients with underlying diseases and complication that may cause the disorder, and patients medicated with drugs that may affect the swallowing ability require appropriate management by medical care staff.