Black stools might suggest stomach cancer, but most cases are not. Often, factors such as diet structure and medications can lead to transient black stools, which are physiological. For instance, consuming animal blood, foods containing pigments, and certain medications like blood tonics and bismuth drugs protecting the stomach lining can cause transient black stools. Once dietary adjustments are made or related medications are stopped, the stool color usually returns to normal. In pathological conditions, such as acute gastric mucosal lesions and bleeding from gastric or duodenal ulcers, black stools can also occur. Thus, the occurrence of black stools might suggest the possibility of stomach cancer, but in most cases, it likely is not.