The purposes of this study are (1) to determine the factors associated with blood glucose control, (2) to ascertain how coping strategies change over time. 63 diabetic teenagers completed four questionnaires of daily stress, diabetic stress, coping and self-care behaviors in 1994. 55 out of 63 diabetic teenagers completed the same questionnaires again in 1995, and 39 among 55 subjects were compared longitudinally at 3-points (1992, 1994, 1995 year) on coping, HbA1c and C-peptide. Using multiple regression on 63 subjects, six factors (self-care behaviors, C-peptide, coping of "drink beer, wine, liquor", "eat food", "Engaging in demanding activity", diabetic stress) accounted for 55% of the variance in control of blood glucouse levels. The 2 points-time (1994 and 1995 year) correlations of stress, coping, self-care behaviors and HbA1c were all highly correlated, whereas the 3 points-time (1992, 1994 and 1995 year) correlations of coping were different in each coping pattern. "Seeking friendly support", "Ventilating feeling" and "Solving family problems" had higher correlations, and "Engaging in demanding activity" and "Optimistic definition of the situation" had lower correlations. Using matched t-test in the 2 points-time, it was found that the total score of stress and "Seeking friendly support" increased significantly between 1994 and 1995. Between 1992 and 1994, HbA1c became higher, and C-peptide and "Relaxing" decreased. The findings of this study suggested that nursing intervention to increase coping of "Engagingin demanding activity", and to decrease stress are necessary in order to maintain good blood glucose control in teenagers with insulin-dependent diabetes mellitus.