Phase II of a study on the effectiveness of B. Feingold's recommended diet for hyperactive children involved the nine children (mean age 9 years) who had shown the "best" response to diet manipulation in Phase I. Each child served as his own control and was challenged with specified amounts of placebo and artificial color containing food items while being maintained on a strict elimination (Feingold) diet over an 11-week period. Parental and teacher ratings, classroom behavior observations, and neurological test scores obtained during baseline, placebo, and challenge conditions were not found to be adversely affected by the artificial color challenge materials. Comparable data gathered on a matched control group showed them to receive significantly better ratings than the hyperactive Ss on the majority of the comparison measures employed. Possible explanations for the discrepancy between the dramatic clinical-anecdotal reports that have been given and the more equivocal findings from formal experimental projects were considered. (Tables, graphs, and charts with statistical data are included.) (SBH)