Studies in well-defined populations are useful in identifying factors that influence frequency and severity of headache and in understanding its impact on people. The aims of this study were to determine the frequency of headache in the medical students of Santa Catarina's Federal University, examine associated factors, verify the diagnostic impressions of the different types of headache, and describe the self-medication level. This study included 408 medical students who were interviewed by a questionnaire from October 1997 to August 1998. The frequency of headache in this group was 33%, with women and students in the five last semesters of the medical course experiencing increased headache frequency. The diagnostic impressions of the different types of headache were migraine without aura (31.3%), migraine with aura (8.2%), episodic tension-type headache (32.1%), chronic tension-type headache (7.5%), and tension-type headache combined with migraine without aura (3%). Self-medication was reported by 51.8% of the medical students with headache; 34.4% used prescribed medications. The most common self-help techniques used by students during a headache were to lie down or isolate themselves from their surroundings.