Blood fatty acid status and visual function of 20 treated hyperphenylalaninemic (HPA) children, randomly allocated into two groups to receive supplementation of either long chain polyunsaturated fatty acids (LCPUFA), including docosahexaenoic acid (DHA), or placebo for 12 months, have been investigated three years after the end of the treatment. Although in the LCPUFA group blood DHA levels and P100 wave latency improved at the end of supplementation, they had returned to baseline after three years.