There are many types of miscellaneous primary headache, but two groups have been selected for discussion: trigeminal autonomic cephalalgias (TAC) and cephalalgias without autonomic dysfunction(CWAD). TAC are strictly unilateral and CWAD are usually bilateral. Sudden onset and relatively short duration characterize most,but some are frightening to patient and doctor alike. One, thunderclap headache, is symptomatic until proven otherwise. Although the others are rarely symptomatic, therapy can be difficult until it is recognized that diagnosis often predicts treatment.