Headaches are extremely common. In most cases, headaches bother the person who has them far more than they bother the physician who treats them. This is because headaches rarely indicate severe or progressive disease. Most headaches occur when the muscles that cover the top of the skull contract. These headaches, called tension headaches, occur off and on in everyone. They go away either by themselves or with simple drugs such as aspirin, acetaminophen, ibuprofen, or any of a multitude of drugs that contain combinations of these drugs.     A less common but more painful type of headache, called a migraine or a cluster headache, results when the arteries of the scalp contract. These headaches may be severe, may involve only one side of the head, and may occur along with nausea, vomiting, and changes in vision. Such headaches tend to recur and often require prescription drugs that relax the contractions of the arteries.     Another common cause of headaches is a generalized illness such as influenza or infections in the sinuses or ears. Sinus headaches are especially common in people with HIV infection, who frequently have sinusitis.     Finally, headaches may result from certain drugs, including AZT, trimethoprim-sulfamethoxazole, rifampin, ketoconazole, amphotericin B) and acyclovir.     All of these headaches go away by themselves, leave no impairment behind, and do not indicate any serious underlying disease.     Certain headaches, however, require a doctor’s attention. Like other focal neurologic symptoms and like fever and stiff neck (see below), headaches can be a symptom of an infection of the brain or the meninges. Headaches associated with infections of the brain or meninges have the following characteristics:1.  They are unusually severe or last unusually long.2.  Either the character of the pain or the location of pain makes the headache different from headaches the person usually has.3.  They occur along with problems with vision.4. They occur along with weakness of an arm or leg, with dizziness, or with impaired coordination.5.   They occur along with stiff neck, nausea and vomiting, or extreme lethargy or sleepiness.6.   They are severe and occur along with an unexplained fever.     The major infections that cause such headaches in people with HIV infection are toxoplasmic encephalitis and cryptococcal meningitis. Both these infections, as well as a multitude of other infections of the brain and meninges, are relatively easy to diagnose. They are also treatable. A less common cause of headaches in people with HIV infection is lymphoma.*131\191\2*