The purpose of this study was to examine the reliability and construct validity of Kearney and Fleischer's (1979) Exercise of Self-Care Agency Scale. The Self-Directed Learning Readiness Scale (SDLRS) (Guglielmino, 1977) was used to test construct validity. Subjects consisted of 62 post-basic nursing students and 57 adult diabetic patients. The results showed significant correlations between the scales for both groups. However, the relationship was stronger for the student group (r = 0.505) than for the patient group (r = 0.302). The Exercise of Self-Control Agency Scale was significantly correlated with all eight factors of the SDLRS for the student group and with only three factors for the patient group. Split-half reliability for the former scale was similar for both groups (r = 0.78 and 0.74); test-retest reliability was lower for the patient group (r = 0.55) than for the student group (r = 0.76).