In order to find out whether patient-controlled sedation carried out only prior to surgery was sufficient for patients to undergo minor oral surgery, 30 patients of either sex between the ages of 16 and 30 years were selected. Each was scheduled to undergo bilateral third molar surgery, one side only at a visit. At the first visit each patient was randomly allocated to receive patient-controlled sedation with midazolam either only prior to, or to the end of surgery. At the second visit they received the alternative method of sedation when the operation was carried out on the opposite side. With both techniques the majority of the patients were relaxed and provided good operating conditions with stable vital signs and without loss of consciousness. However, when given the opportunity to sedate themselves until the end of surgery, 70 per cent obtained increments during surgery; four were assessed to have marked sedation and in five the button dropped off. When questioned at the end of both procedures, 87 per cent preferred to have increments during surgery.