Digestion is a complex process regulated by several factors. Among these, one of the most important is the time of gastric emptying. A delayed gastric emptying time can be caused by several factors and can generate considerable discomfort in humans. It ranges from mild to real debilitating disorders. Until now, different tests are suggested to study the gastric emptying time. The present review presents the mayor cause and the main symptoms linked to delayed gastric emptying and will focus on the (13)C-octanoid acid breath test, as a good candidate for studying solid gastric emptying time.