Eighty-four persons with insulin-dependent diabetes participated in this study to determine whether glycemic control was related to personality, anxiety, depression, and/or quality of life. The subjects were placed on either a conventional treatment regimen consisting of one to two injections of mixed short and intermediate-acting insulin, with urine testing or an intensive treatment regimen consisting of two or more injections of mixed insulins, with self-monitoring of blood glucose. Personality was found to have no relationship to level of glycemic control either at the beginning of the study or at any point during the study. In contrast, anxiety, depression, and quality of life showed a significant relationship to metabolic control at entry and throughout the study period. Lower anxiety and depression scores and better quality of life scores were recorded for those subjects in good control (HbA1 < 8.9%) when compared with those in average control (HbA1 9.0–11.9%) and those in poor control (HbA1 > 11.9%) at entry (P = 0.01). At each point during the study the difference between those in good control and those in poor controlin terms of anxiety, depression, and quality of life was significant (P = 0.02). Change in glycemic control was found to account for up to 20% of the between-patient variability for these psychosocial parameters.