To evaluate the association of anaesthesia and surgery with postoperative headache in elective surgery patients By multiple logistic regression analysis of data collected during a six-month period from 446 patients undergoing elective surgery, a prospective single centre cohort study in a university hospital. Participants were interviewed preoperatively and for five days postoperatively regarding the appearance of headache; while demographics, life style, type of anaesthesia and surgery, the anaesthetic drugs administered and intraoperative adverse effects in elective surgery patients are recorded.