The Obesity Reduction Black Intervention Trial (ORBIT) is a randomized controlled trial designed to assess the efficacy of a culturally proficient 6-month weight loss intervention followed by a 1-year maintenance intervention. This article describes the results of the 6-month weight loss intervention. Two hundred thirteen obese black women aged 30-65 years were randomized to the intervention group or a general health control group. The intervention consisted of a 6-month culturally adapted weight loss program that targeted changes in diet and physical activity patterns. Weight, dietary intake, and physical activity were measured at baseline and 6 months. A total of 198 women (93%) completed both the baseline and postintervention assessments. Women in the intervention group lost significantly more weight than women in the control group (P < 0.001). However, weight change was variable within the intervention group, with a maximum weight loss of 19.4% of initial body weight and a maximum weight gain of 6.4% of initial body weight. Women in the intervention group also showed significant improvements in fruit intake (P < 0.01), Healthy Eating Index score (P < 0.001), and moderate (P = 0.05), and vigorous (P < 0.001) physical activity compared to women in the control group. This study demonstrates that a culturally adapted program can successfully promote weight loss in obese black women. However, average weight loss was relatively modest, and weight change varied widely within the intervention group. Further research is needed in order to develop programs that will allow more black women to achieve their weight loss goals..