Many chronic heart failure patients are hospitalized repeatedly because many of them are still uncertain about the methods necessary for managing their own health. "Self-monitoring" is a useful concept for breaking through this vicious cycle. However, there are no suitable tools to measure aspects of self- monitoring. This study aimed at the development of an evaluation scale for self-monitoring by patients with chronic heart failure based on the concept of self-monitoring. Outpatient with chronic heart failure completed a self-administered scale comprises 2 domains and covers 38 items. Domain 1 deals with "awareness" and "measurement" of aspects of self-monitoring, domain 2 with "interpretation" of aspects of self-monitoring. The reliability and validity of this scale were thoroughly evaluated. Of the 167 patients asked to participate in the study, 142 gave valid responses. Factor analysis showed that the domain1 comprised six factors (21 items) and the domain2 four factors (16 items). Cronbach's α coefficient was 0.91 for domain1, 0.89 for domain2. The intra-class correlation coefficient of total score was 0.74 for domain1, 0.67 for domain2. Concurrent validity with the Heart Failure Self-care Behavior Scale was demonstrated. The scale is reasonably reliable and valid, and was proved to be useful for assessing conditions related to patient self-monitoring. Since it has become an indicator that shows to what degree patients can perceive their own health status, and nurses have been utilizing it to provide individual support to reduce the risks of exacerbated heart failure.