If patients with PKU follow a strict diet low in phenylalanine from soon after birth their intellectual and psychomotor development will be within the normal range. Recent studies have shown that it is necessary to continue the burdensome diet throughout one's life. This is in contrast to past practice and puts additional emphasis on psychosocial aspects of PKU. In the present retrospective study we investigated how adolescent patients and their relatives' experience and cope with this chronic disease.