Generic drugs are significantly less expensive than their brand name counterparts, and the use of generic drugs has increased drastically in recent years, representing upwards of 75% of all prescriptions filled in the United States. A large amount of this increase is due to states' adoptions of generic substitution laws, or laws that allow for the substitution of generic drug formulations in place of their brand name counterparts. Theoretically, generic drugs are just as effective as their brand name alternatives; in fact, the FDA requires that generic formulations demonstrate "bioequivalence," meaning that they show absorption rates of active ingredients that are within a range of 80-125% of that of brand name drugs. Despite their theoretical equivalence, generic and brand name drugs can produce disparate results and side effects. This is problematic when states employ substitution schemes in which no notification of either the physician or patient is necessary for the pharmacist to substitute, and is especially problematic when these conditions are met and substitution is mandated. This problem may be exacerbated for individuals with chronic mental illness, where reduced effectiveness of generic medications can produce individually and societally detrimental outcomes and where differential side effects might interfere with already poor medication compliance rates. This Article examines the effectiveness of generic versus brand name drug formulations in terms of treating mental illness, discusses possible implications of their differential effectiveness, and proposes several solutions for policy change to combat these issues.