We have developed a simple but reliable method for assessing gastric emptying, a sulfamethizole capsule food method. The capsule food contains egg albumin and sulfamethizole. In saline or hydrochloride solution only a small amount of sulfamethizole, in sodium bicarbonate solution, however, a large amount of the drug was released from the capsule food. In this method, sulfamethizole concentrations in blood were measured in subjects after ingestion of 15 pieces of capsule food containing 1.0 g of sulfamethizole, and area under the curve of the blood concentrations was calculated as an index of gastric emptying. Gastric emptying of capsule food had a lag phase of 15 minutes, which was already reported in gastric emptying of radioisotope labeled solid food. Bread combined with the capsule food caused a delay in gastric emptying and a larger volume of the bread was associated with a longer gastric emptying time. In conclusion, our sulfamethizole capsule food method is useful in clinical practice to assess gastric emptying of solid food.