The effect of applying nitroglycerin or placebo ointment to the back of the hand before venipuncture and injection of propofol was investigated in 60 ASA physical status I unpremedicated women. Eighteen patients (67%) pretreated with nitroglycerin experienced no pain compared with 10 (33%) in the placebo group. Eleven in the placebo group experienced moderate or severe pain during injection compared with only one in the active group. The time of onset of pain in more than half the subjects occurred 10 s or longer after commencement of injection, and, in more than half the patients, the site at which pain was felt was above the injection site (with three subjects experiencing it in the shoulder). No patient had a headache or experienced postural hypotension. We conclude that nitroglycerin ointment applied to the back of the hand before injection reduces the incidence of painful injection with propofol.