This study aimed at investigating the relation between psychological diabetes-related health behavior, and metabolic aspects of diabetes. Fifty-one adult patients with type I diabetes mellitus took part in the study. Psychological status, health, and self-care behavior were assessed by means of questionnaires. Level of glycosylated hemoglobin (HbA(1c) served as the index of metabolic control. Depression was slightly elevated among women as was trait anxiety and blood-injury phobia or fear of medical interventions in all patients. Depression and anxiety were not related to duration of diabetes or presence of diabetes complications. As could be expected, patients who frequently checked their blood glucose level had a significantly lower level of HbA(1c) than those with infrequent checks. Patients with a marked blood-injury phobia carried out fewer daily checks of blood glucose level than those without, but blood-injury phobia was not directly related to HbA(tc) level. A higher level of HbA(tc) was, however, associated with mood deterioration. As depression was not related to health behavior, its effect on metabolic control is likely to be mediated via endocrine rather than behavioral variables.