Data from the U.S. Centers for Medicare and Medicaid Services' Medicaid database were analyzed to define recent trends in the use and cost of opioid medications United States as a whole and in seven states between 1998 and 2003. Over this time period, total Medicaid prescriptions for opioids have nearly doubled and, in nominal terms, expenditures have nearly tripled. The morphine derivatives account for the largest share of these increases. By 2003, opioids represented about a four percent share of all Medicaid prescription drugs. Variations among the states in per-enrollee spending on opioids are substantial. The appropriateness of these variations is unknown.