Congress is considering enactment of comprehensive parity legislation. The intent of parity is to equalize private coverage of behavioral and general medical care, thereby improving efficiency and fairness in insurance markets. One issue is whether to extend parity to substance abuse (SA) benefits. In the past, inclusion of substance abuse has been a hurdle to passage of parity. We examine the politics of SA parity, compare coverage trends for substance abuse and mental health, and assess the rationale for equalizing benefits. We conclude that the justification for SA parity is as compelling as it is for mental health parity.