We assessed the effect of two different doses of alfentanil (5 and 10 micrograms.kg-1) on the conditions for laryngeal mask airway insertion in ASA 1 and 2 patients who received propofol for induction of anaesthesia. One hundred and fifty unpremedicated patients were randomly allocated to receive either propofol 2.5 mg.kg-1 only (Group P), alfentanil 5 micrograms.kg-1 and propofol 2.5 mg.kg-1 (Group A5), or alfentanil 10 micrograms.kg-1 and propofol 2.5 mg.kg-1 (Group A10). The addition of alfentanil to propofol resulted in a greater ease of insertion and a better quality of airway patency. Pretreatment with alfentanil also resulted in a significantly higher success rate during the first attempt at inserting the laryngeal mask airway compared with Group P (Group P 58%, Group A5 96%, Group A10 94%). Patients in Group P were apnoeic for a mean (+/- SD) time of 3.3(+/- 1.9) min, 4.71 (+/- 2.2) min in Group A5, and 7.32(+/- 4.3) min in Group A10. The use of alfentanil 10 micrograms.kg-1 with propofol, however, led to a significant decrease in mean arterial pressure and heart rate. We concluded that pretreatment with intravenous alfentanil 5 micrograms.kg-1 prior to propofol provides excellent conditions for insertion of laryngeal mask with minimal adverse haemodynamic changes.