The aim of this study was to investigate the incidence of pre-induction coughing, after an iv bolus of fentanyl. The study sample was 250 ASA physical status I-II patients, scheduled for various elective surgical procedures. The first 100 were randomly allocated to receive 1.5 micrograms.kg-1 fentanyl via a peripheral venous cannula (Group 1), or an equivalent volume of saline (Group 2). Twenty-eight per cent of patients who received fentanyl, but none given saline, coughed within one minute (P less than 0.0001). The second 150 patients were then randomly assigned to three equal pretreatment groups. Group 3 received 0.01 mg.kg-1 atropine iv one minute before fentanyl. Groups 4 and 5 received 0.2 mg.kg-1 morphine im, and 7.5 mg midazolam po, respectively, one hour before fentanyl. Thirty per cent of patients in Group 3, 6% in Group 4, and 40% in Group 5, had a cough response to fentanyl. Fentanyl, when given through a peripheral cannula, provoked cough in a considerable proportion of patients. This was not altered by premedication with atropine or midazolam, but was reduced after morphine (P less than 0.01). Coughing upon induction of anaesthesia is undesirable in some patients, and stimulation of cough by fentanyl in unpremedicated patients may be of clinical importance.