To be the master of their disease and not its slave is the ultimate goal of many patients with diabetes. Intensified functional insulin therapy (FIT) helps to establish this goal by an intensive patient education: each patient learns in five small-group sessions how s/he reacts to standardized challenges of glucose homeostasis (e.g. 24 h fasting; physical exercise; various carbohydrate loads). We investigated in 43 patients with long-standing diabetes type 1 (mean age: 33 +/- 10 years; mean duration of diabetes: 15 +/- 10 years) whether FIT improves quality of life, influences metabolic control and doctor-patient relationship. The following instruments were used: diabetes specific quality of life questionnaire (DQOL), hierarchical distance and cohesion between doctor and patient (FAST), anxiety and depression (HAD). Pre and post intervention values were compared with paired t-tests. HbA1c and number of hypoglycaemic episodes were also assessed 1 year after FIT and 1 year prior to FIT. Metabolic control was improved: HbA1c in the year before FIT: 6.72 +/- 1.35; 4 months before FIT: 6.61 +/- 1.46; 4 months after FIT: 6.29 +/- 1.09 (P < 0.05 compared to 4 months before FIT); 1 year after FIT: 6.46 +/- 1.12 (n.s. compared to 1 year before FIT). Dissatisfaction with life decreases from 33.3 +/- 8.0 to 28.5 +/- 7.7 (P < 0.001). Moments free of disease-specific strain increase from 74.3 +/- 13.9 to 78.1 +/- 16.1 (P = 0.07). Hierarchical distance between doctor and patient decreases from 1.1 +/- to 0.6 +/- 0.8 (P < 0.001), cohesion increases from 9.3 +/- 1.5 to 9.9 +/- 1.1 (P < 0.001). Anxiety and depression both decreases significantly: anxiety, 6.5 +/- 3.3-->4.6 +/- 3.2 (P < 0.001); depression, 2.7 +/- 2.5-->1.5 +/- 1.6 (P < 0.001). The number of patients with severe hypoglycaemic episodes (level 4) decreases from five (11.6%) to one (2.3%) after intervention (P < 0.05). In conclusion, FIT enhances quality of life in diabetic individuals. It helps to establish a less hierarchical and closer relationship between patient and doctor as revealed by the FAST data. It should be emphasized that the psychological improvements are not achieved at the expense of less strict metabolic control.