To determine whether morning headaches are a consistent symptom in sleep apnea, we reviewed clinical and polysomnographic data of 304 patients with sleep apnea and compared the findings with normal control subjects and with three other groups of patients seen at a sleep disorders center. Eighteen percent of patients with sleep apnea had frequent morning headaches compared with 21% to 38% in the other groups of patients and 6% of control subjects. In patients with sleep apnea, morning headaches were most common in those with mild predominantly nonobstructive apnea. Polysomnographic characteristics of patients with moderate to severe sleep apnea did not significantly differ between patients with frequent headaches and those without such headaches. Frequent morning headaches are a nonspecific symptom in patients with sleep disorders and are not a consistent or reliable symptom of sleep apnea syndrome.