Rising overweight and obesity rates in the United States and the accompanying health issues underscore the need for an effective treatment for weight loss. While most people tend to lose weight as a result of cognitive-behavioral treatment, the weight is often regained after treatment ends. Possible reasons for weight regain include not fully integrating lifestyle changes necessary to maintain weight loss and lack of motivation to continue treatment. One way to augment the efficacy of cognitive-behavioral treatments for weight loss is to combine it with hypnosis, which has been shown to improve motivation and adherence to treatment. The current study assessed the efficacy of hypnosis as an adjunct to a standard cognitive-behavioral program for the treatment of obesity. Weight loss was compared between participants who received the standard cognitive-behavioral treatment (CBT), those who received hypnosis in addition to the standard cognitive-behavioral treatment (H-CBT), and a minimal treatment control group focusing on nutrition and exercise information (C). Treatment consisted of eight consecutive weekly group sessions of 1.5 hours and weight was recorded at the beginning of each session. The results of the ANOVA indicate that there are no statistically significant differences between the three treatment groups, F(2,22) = 1.161, p = 0.334. However, the study lacked sufficient power to detect statistical significance and effect sizes were calculated. A large effect size (d = 0.85) was found between H-CBT and C, a moderate effect size (d = 0.61) was found between CBT and C, and a small effect size (d = 0.28) was found between H-CBT and CBT. Thus, both the H-CBT group and the CBT group outperformed the minimal treatment group, H-CBT to a large degree and CBT to a moderate degree. While only a small effect size was found between H-CBT and CBT, the result indicates that the use of hypnosis improves a cognitive-behavioral treatment for weight loss and this is very meaningful when considering the robust nature of overweight and obesity. Future studies should include follow-up data to determine whether the use of hypnosis improves the long-term maintenance of weight loss. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]