BACKGROUND: Prescriber requirements are a form of utilization management (UM) in which health plans require that a certain type of physician (eg, a rheumatologist) prescribe a drug. OBJECTIVE: To examine how a set of US commercial health plans impose prescriber requirements in their specialty drug coverage decisions. METHODS: We identified specialty drug coverage decisions from the Tufts Medical Center Specialty Drug Evidence and Coverage (SPEC) Database. SPEC includes coverage information issued by 17 large US commercial health plans. We categorized prescriber requirements as the following: (1) the drug must be prescribed in consultation, supervision, or coordination with a specialist; (2) the drug must be prescribed by a specialist (eg, a neurologist); or (3) the drug must be prescribed by a specialist with particular expertise (eg, a neurologist with expertise in spinal muscular atrophy). First, we examined how often each plan imposed prescriber requirements. Second, we determined the degree of specialization that plans required prescribing physicians to have. Third, we used Pearson's chi-square tests to examine the association between plans' use of prescriber requirements and the following drug characteristics: cancer treatment, orphan indication, pediatric indication, drug approved in the last year, black box warning, and self-administered formulation. RESULTS: Overall, health plans imposed prescriber requirements in 22.0% (1,844/8,383) of their coverage decisions, although the frequency that they did so varied (range: 0.8%-86.0%). Of prescriber requirements, 79.1% (1,459/1,844) required that the drug be prescribed in consultation, supervision, or coordination with a specialist; 18.3% (338/1,844) required that the drug be prescribed by a specialist; and 2.6% (47/1,844) required that the drug be prescribed by a specialist with particular expertise. Plans were more likely to impose prescriber requirements for drugs with the following characteristics: indicated for a pediatric population, black box warning, self-administered, and noncancer treatments (all P < 0.001). CONCLUSIONS: Health plans varied in the frequency that they imposed prescriber requirements in their specialty drug coverage decisions and with respect to the degree of specialization they required prescribing physicians to have. DISCLOSURES: This study was funded by the Center for the Evaluation of Value and Risk in Health at Tufts Medical Center. The center receives funding from a variety of sources, including government agencies, foundations, and pharmaceutical and device companies. The SPEC Database, which provided data for this study, is funded in part through a data subscription program to which a number of pharmaceutical companies subscribe. All authors are employed by the Center for the Evaluation of Value and Risk in Health. In addition, Chambers reports speaker fees from Astellas and consulting fees from Biogen and Lundbeck. The other authors have nothing to disclose. An earlier version of this study was presented as a poster at the AMCP 2021 Virtual Meeting, April 12-16, 2021.