A single-subject design was used to investigate the impact of a dietary change on the emotional state of four individuals selected by means of the Behavioral Index of Metabolic Imbalance and a subsequent interview. The dietary change for three subjects consisted of a high protein-low carbohydrate diet void of sucrose and caffeine, whereas only caffeine and sucrose were eliminated for the fourth subject. The dependent variable used with the first subject was a self-report of symptoms experienced, whereas the Minnesota Multiphasic Personality Inventory (MMPI) and the Profile of Mood State (POMS) were used with the other subjects. Results revealed that subjects reported many symptoms and/or presented a distressed profile during baseline assessment. However, following a 2-week dietary change symptoms declined, and the MMPI or POMS profiles reflected a more stable and less distressed individual. Overall, the results suggest that a dietary change can remediate the emotional distress exhibited by some individuals. During the past decade the public has become increasingly aware that diet can have an impact on behavior. This awareness has arisen primarily through the publication of books (e.g., Feingold, 1972) that have hypothesized an association between behaviors such as hyperactivity and dietary elements such as food colors and preservatives. Although such associations have generally not been substantiated (Conners, 1980), additional evidence, which seems to support a possible diet-behavior relationship, has increasingly appeared in the literature. Kwok (1968) described the adverse behavioral effects, for example, headache and nausea, that can occur from the ingestion of monosodium L-glutamate. Green (1969), Powers (1973), and Von Hilsheimer (1974) reported case studies of children whose behavioral disturbances, irritability, hyperactivity, and short attention span improved following a dietary change consisting of a high-protein/ low-carbohydrate diet and the inclusion of various vitamin supplements. Mikkelsen (1978), Greden (1974), and others have reported that paranoid delusions, headaches, anxiety symptoms, depression, and insomnia have been eliminated or dramatically reduced following the elimination or a reduction in the amount of caffeine consumed.