Objective. To determine the headache prevalence like main reason of consultation, primary and secondary headaches and alarm signs in Emergency Service. Patients and methods. It was carried out a serial sampling in the Emergency Service of the Clínica Los Comuneros in Bucaramanga, since the 6th to 15th December of 2002, including all patients older than 18 years old, were excluded pregnant women and patient with mental retardation, psychotic disorders or dementia. Results. 100 patients out of 1,054 consulted for headache (9.49%); 25% corresponded to primary and 75% to secondary headaches. Thirty four patients had fever, headache began after the 50 years in 7, signs and focal symptoms in 4, cancer antecedent in 4, mental changes in 3, antecedent of trauma cranial in 2, thunderclap headache, headache persistently unilateral, antecedent of AIDS and signs meningeal in a patient respectively. Conclusions. The headache is a reason of frequent consultation in the Service of Emergency; the proportion of secondary headaches is high.