OBJECTIVE - To examine psychometric properties of the Confidence in Diabetes Self-Care (CIDS) scale, a newly developed instrument assessing diabetes-specific self-efficacy in Dutch and U.S. patients with type 1 diabetes. RESEARCH DESIGN AND METHODS - Reliability and validity of the CIDS scale were evaluated in Dutch (n = 151) and U.S. (n = 190) outpatients with type 1 diabetes. In addition to the CIDS scale, assessment included HbA1c, emotional distress, fear of hypoglycemia, self-esteem, anxiety, depression, and self-care behavior. The Dutch sample completed additional measures on perceived burden and importance of self-care. Test-retest reliability was established in a second Dutch sample (n = 62). RESULTS - Internal consistency (Cronbach's α = 0.86 for Dutch patients and 0.90 U.S. patients) and test-retest reliability (Spearman's r = 0.85, P < 0.0001) of the CIDS scale were high. Exploratory factor analysis showed one strong general factor. Spearman's correlations between the CIDS scale and other measures were moderate and in the expected directions, and high HbA1c levels were associated with low CIDS scores in the U.S. sample only. Low CIDS scores were positively associated with self-care but not with glycemic control in the original samples. CIDS scores in the U.S. and Dutch samples did not show any statistically significant differences. U.S. men had higher CIDS scores than U.S. women. CONCLUSIONS - The CIDS scale is a reliable and valid measure of diabetes-specific self-efficacy for use in patients with type 1 diabetes. High psychometric similarity allows for cross-cultural comparisons.