Background: Percutaneous endoscopic gastrostomy (PEG) is generally used for long-term enteral nutrition. Patients who require PEG placement are often very sick, and postoperative complications, especially aspiration pneumonia, can be fatal. Objective: In this study we investigated the risk factors for aspiration pneumonia after PEG using a simple two-step swallowing provocation test (S-SPT), as reported in 1999 by Teramoto et al. Methods: The study included 29 patients (10 men, 19 women; mean age 84.6 years) who underwent S-SPT before PEG. We evaluated the presence of reflux esophagitis (RE) and esophageal hiatal hernia (EHH) with PEG. According to the S-SPT results, a normal response to the 1st step S-SPT was given a score of 0, a normal response to the 2nd step S-SPT was given a score of 1, and an abnormal response to the 2nd step S-SPT was given a score of 3. In addition to S-SPT, the presence of RE was given a score of 3, the absence of RE was given a score of 0, the presence of EHH was given a score of 2, and the absence of EHH was given a score of 0. We evaluated the association between the presence of aspiration pneumonia, as an early and critical complication, up to 1 month after PEG and determined the total risk score (score of S-SPT+ score of RE+ score of EHH). Results: The group with an abnormal response to the 2nd step S-SPT and the group with RE both exhibited aspiration pneumonia. The patients with aspiration pneumonia all achieved total scores ≧3, and 8 of 13 patients without aspiration pneumonia achieved scores ≤2. Conclusions: S-SPT is particularly useful in PEG patients. The scores provided by S-SPT and endoscopic examination can be very useful for aspiration pneumonia after PEG. The patients with scores ≤2 appear to be at very low risk for aspiration pneumonia, and patients with the scores ≧3 should be carefully followed up.