This chapter suggests that U.S. initiatives to develop and deploy active strategic defenses, including ballistic missile defense (BMD), are not necessarily inconsistent with U.S.-Soviet nuclear arms control. Much expert opinion is skeptical of the compatibility of the Reagan Strategic Defense Initiative (SDI) and arms control. The prognosis for any U.S. theater or strategic BMD may be more pessimistic to the extent that it is considered incompatible with arms control agreements that improve strategic stability.