Reported are findings of a study involving 46 families in which the effect of the Feingold (additive free) diet on hyperactivity in preschool and elementary age children was investigated. Eleven sections cover the following project components: introduction (definition of hyperactivity and the B. Feingold hypothesis), methodology, demographic information, physical-neurological examination results, nutrient analysis, classroom and laboratory observations, reaction time, Continuous Performance Test results, neuropsychological tests, behavioral ratings, and the preschool sample. It is reported in a summary that with the possible exception of a small preschool sample on whom limited data could be obtained, the overall results did not provide convincing support for the efficacy of the experimental (Feingold) diet, and that the frequency with which favorable diet effects were judged to be present was highest in the subjective parent ratings, declined sharply in the teacher ratings, and essentially disappeared in the objective neuropsychological, classroom, and laboratory observational data. Included are charts, graphs, and tables with statistical data. (SBH)