Headache and acquired immunodeficiency syndrome. Because the acquired immunodeficiency syndrome (AIDS) virus is neurotropic, physicians will continue to see a rise in the number of neurologic complications of this syndrome. Much of this increase will be accompanied by headache, not only as a primary symptom of HIV infection or opportunistic disease but also as a result of diagnostic tests and therapeutic efforts. Complete understanding of the ramifications of headache in AIDS will be important in the 1990s as we continue to treat a younger population, usually affected by benign vascular and muscle contraction-type headache. 