The results of the first 10 years of a prospective study of the effect of corn-oil and standard diets given to diabetic children since diagnosis suggest that the corn-oil diets currently available in Britain are not acceptable to most diabetic children and adolescents. Attempts to administer such diets may result in hyperpre-beta-lipoproteinaemia. In most diabetic children normal serum lipid levels can be maintained with adequate diabetic control and a standard diabetic diet.