This study examined the effectiveness of the addition of a cognitive intervention based on individualized assessment to a behavioral intervention for obesity. Overweight subjects (N=63) were randomly assigned to either a behavioral intervention or a behavioral intervention combined with a cognitive intervention which focused on changing specific maladaptive self-statements related to weight loss. Physiological, behavioral, and cognitive measures were used to assess change between pretest, posttest, and 3-month follow-up. The hypothesis that behavioral and cognitive intervention would result in greater weight loss and reduction in body fat than the behavioral intervention alone was not supported at posttest or at follow-up. The hypothesis that both treatments would show significant differences between time points on behavioral measures was supported. Two hypotheses examined the construct validity of the cognitive intervention and the generalizability of the cognitive intervention. Both conditions showed changes over time on cognitive measures, but differences between the treatments were not significant. Future research on the effectiveness of cognitive interventions in the area of weight loss should include measures other than those that are weight-related, longer follow-ups, and sufficient amounts of cognitive therapy to allow clients to fully integrate the cognitive dialogues into their everyday lives. (Author/NB)