Specialty drugs are expensive, but spending on specialty drugs is difficult to measure because of proprietary rebate payments by manufacturers to insurers, pharmacy benefit managers, and state Medicaid agencies. Our study extends recent research that documented growing use of and spending on specialty drugs by incorporating manufacturer rebates for both public and private payers. Although specialty drugs make up a small portion of retail prescriptions filled, we found that they accounted for 37.7 percent of retail and mail-order prescription spending net of rebates in 2016-17. From 2010-11 to 2016-17, spending net of rebates tripled for Medicare Part D beneficiaries and more than doubled for people with private insurance. Medicaid spending net of rebates rose more slowly. These results can help inform decision makers as they strive to balance the costs and benefits of innovative drugs.