We examined 2001 prescription drug claims for a range of employer-based retiree plans administered by a national pharmacy benefit management firm, to understand how use and spending differ with various cost-sharing approaches and other drug use management techniques among the elderly. In these plans, most of which had generous benefits and substantial use of mail order, more aggressive cost-sharing requirements combined with other management strategies were associated with greater member cost sharing, a shift to less costly medications (generic and mail order), and lower total prescription drug spending. Although we did not find lower rates of use in plans with aggressive cost sharing, this may be attributable in part to their higher drug use associated with mail-order incentives.