To ascertain the quality of life associated with the health state of diabetes mellitus using utility value analysis. Consecutive adult patients with diabetes mellitus for at least 1 year and a mean age of 61.7 years (range 21-85 years) were interviewed in a cross-sectional fashion using standardized research methodology. Utility analysis values were obtained employing the time tradeoff method and were correlated with clinical parameters of the sample group, as well as with co-morbidities using the heteroscedastic Student's t-test and multivariate linear regression. The chi(2) distribution to test for independence was used to compare sample subgroups. With a sample of 292 patients, the mean, patient-preference-based, time tradeoff utility value associated with the health state of diabetes mellitus was 0.88 (standard deviation (SD)=0.17; 95% confidence interval (CI), 0.86-0.90). Repeat analysis confirmed the reproducibility of the data. Thus, the average diabetic was willing to trade away 12% of his or her remaining life in return for a diabetic-free health state. Factors associated with a significant decrease in diabetic-associated quality of life included: (1) the requirement for insulin (p=0.05), (2) the presence of depression (p=0.01), (3) the presence of diabetic retinopathy (p=0.03) and the presence of co-morbidities in general (p=0.01). The health state of diabetes mellitus has a significant effect upon patient, preference-based quality of life. The presence of diabetic co-morbidities and dependence upon insulin appear to decrease quality of life. The utility value associated with the health state of diabetes mellitus is of substantial importance for use in the calculation of cost-effective analyses.