The Subjective Drug Value procedure (SDV) involves a series of independent, theoretical forced choices between the drug administered and different monetary values. Subjects are asked to choose between receiving another dose of the same drug to take home or an envelope containing a specified amount of money, but they do not receive either the drug or the money described in the choices. Depending on the answer to each question, the monetary value in the next question is either higher or lower. At the end of the procedure (generally 6 questions), the procedure estimates the crossover point at which the subject is indifferent between choosing drug and choosing money. The crossover point is the proxy index of reinforcing efficacy that will be used as an outcome measure for estimating abuse potential. This test is adapted from a similar procedure utilized by Griffiths and colleagues (Griffiths, Troisi et al. 1993; Griffiths, Rush et al. 1996).