Cognitive processing in headache associated with sexual Cognitive processing as measured by event-related potentials (ERP) in patients suffering from the explosive subtype of headache associated with sexual activity (HSA type 2) was investigated. Visual ERP were measured in 24 patients with HSA type 2 outside the headache period. The differences of the first and the second part of measurement were evaluated separately to determine the amount of cognitive habituation. Twenty-four sex- and age-matched healthy subjects and 24 patients with migraine without aura served as controls. A missing increase of P3 latency during the second part of the measurement was found in 79% of patients with HSA type 2 and in 75% with migraine, but only in 17% of the healthy controls (P < 0.001). The P3 amplitude was increased during the second part in 71% of patients with HSA type 2 and in 79% with migraine, but only in 33% of the healthy controls (P = 0.02). Mean P3 latency was decreased and mean P3 amplitude was increased during the second part of the measurement in HSA type 2 and in migraine but not in the healthy control group. Patients with HSA type 2 have a loss of cognitive habituation as measured by ERP. This specific information processing is very similar to that in migraine observed in previous studies.