In a randomized double-blind, double-dummy, placebo-, positive-controlled, and crossover designed drug abuse potential study, there are at least 5 treatments in the study, which includes placebo, several doses of a test drug, and several doses of a positive control drug. Study subjects are volunteers with histories of drug abuse. Because placebo responses are used to compare with responses from the positive control group for validating the study, and also used to compare with responses from the test drug for assessing abuse potential, for a successful drug abuse potential study, it is important to accurately assess placebo effect for each endpoint of interest. In this roundtable discussion, we will focus on evaluation of placebo effect and comparisons with placebo arm in drug abuse potential studies.