Both federal and state governments exercise regulatory authority in many of the same policy areas. In enacting new legislation in these shared areas, Congress must provide federal protections, guarantees, or benefits while preserving an appropriate balance between federal and state regulatory authority and responsibility. State efforts can be directed toward federal or nationally shared regulatory objectives through various arrangements, each of which reflects a way to define and issue regulations or standards and assign responsibility for their implementation or enforcement. Regulatory and standard-setting mechanisms for achieving nationwide coverage include (1) fixed federal standards that preempt all state regulatory action, (2) minimum federal standards that preempt less stringent state laws but permit states to establish more stringent standards, (3) the inclusion of federal regulatory provisions in grants or other forms of assistance, (4) cooperative programs in which voluntary national standards are formulated by federal and state officials working together, and (5) widespread state adoption of voluntary standards formulated by quasi-official entities. The first two of these mechanisms involve preemption; the other three represent alternative approaches. Each represents a different combination of federal and state regulatory authority. The mechanisms also offer different options to implementation or enforcement. Furthermore, each standard-setting mechanism offers advantages and disadvantages that reflect the key considerations of federal-state balance in the context of a given national regulatory objective. Shared implementation involves several operational challenges, such as finding the appropriate level of federal oversight, allocating costs between the federal government and the states, potentially increasing the vulnerability of federal agencies to sudden increases in responsibilities and costs, handling variations in implementation from state to state, and adjusting to the new federal-state balance.