This case study reviews the literature related to diet, behavior and learning and describes procedures and results of a change in the diet of an adolescent girl who had an extensive history of problems at home and at school. Studies of nutritional deficiency, nutritional imbalance, allergies, and synthetic food additives are briefly overviewed. Dietary substance linked to behavior problems and the behavioral characteristics of the hyperkinetic child were identified through review of the related literature, and are summarized in Tables 1 and 2. A 45-item behavior checklist was constructed for parent and teacher use in pre- and post-treatment assessment. The child selected for the study was assessed as having trouble on 39 of the 45 checklist items. Treatment consisted of excluding from her diet (for 14 days) food containing sugar, artificial flavor and color, nitrates, salicylates, MSG, and foods to which the subject was allergic. Comparison of pre- and post-treatment checklists indicates that parents and teacher saw dramatic change in the girl's behavior. She was seen to present problems on only 5 of the checklist items at the end of the treatment. Effects were evident by the third day of the diet. Learning was also judged to have improved. Results are seen to be consistent with previous studies of the effects of nutrition on behavior. Further research is recommended. The behavior checklist, treatment diet and results are also appended. (RH)