Frequent headache is associated with a variety of sleep disorders. The authors compared the prevalence of snoring in a group of chronic daily headache (CDH) subjects (n = 206) with a control group of episodic headache subjects (n = 507). Habitual snoring was more common in the CDH subjects than in the control subjects (24 vs 14%; p < 0.05); the difference remained after adjusting for factors related to sleep-disordered breathing (OR = 2.9; p < 0.005). If this association proves causal, sleep-disordered breathing may provide a target for therapeutic interventions for chronic daily headache.