Pain in the left half of the head is observed with migraine, paroxysmal hemicrania, hypnic and cluster headache, vertebrobasilar insufficiency. It is detected at the initial stage of brain tumors, with limited arachnoiditis, Horton's disease, some ENT diseases and pathologies of the cervical spine. It can be acute, dull, prolonged, paroxysmal, pressing, bursting, breaking, pulsating. The cause is established on the basis of complaints, interview data, neurological examination, additional studies. As part of therapeutic measures, NSAIDs, triptans, steroids, caffeine preparations, and physiotherapy are prescribed. Sometimes operations are performed.