Yawning is a stereotyped normal behaviour with unknown physiological role. It can occur in excess due to a large variety of medical conditions. Acute bouts of yawning are an early but unspecific warning sign for supportive measures. Chronic excessive yawning may lead to medical consultations. In this case, medication side effects and excessive daytime sleepiness are the most freequant aetiologies. Epileptic seizures are occasionally followed by post-ictal yawning which lateralizes the seizure origin to the right hemisphere.