In 1977, Massachusetts implemented a requirement that Medicaid recipients obtain a second surgical opinion before elective surgery. Using consultants' reports and surveys, we assessed the initial year's results in metropolitan Boston. Of 2060 Medicaid patients originally advised to undergo one of eight elective surgical procedures, 1591 (77.2 per cent) participated in the mandatory second-opinion consultation program, 10.5 per cent received approval for surgery without a second opinion because of clear indications such as cancer, and 12.3 per cent did not keep or accept appointments for a second opinion. Of the 1591 patients who participated, 88.7 per cent were given second opinions in favor of surgery, and 11.3 per cent were advised against surgery. Eight-two of the 180 patients advised not to have surgery sought a third opinion; the negative second opinion was reversed by the third consultant in 57 of these cases (69.5 per cent). Thus, surgery was rejected by a second or third consultant for only 7.7 per cent of the participating patients. We conclude that many negative second opinions are due to honest disagreement about indications for surgery. We also estimate that although the second-opinion program may produce only modest direct savings in Medicaid expenditures, it probably offers important improvements in the quality of health care.