Colorectal cancer, the third leading cause of cancer-related death in the United States, could largely be prevented if more people had polyps removed via colonoscopies. Embarrassment is one important barrier to colonoscopy, but little is known about embarrassment in this context, and there were no reliable and valid measures of this construct. The purpose of this study was to develop a reliable and valid instrument to measure colonoscopy-related embarrassment. Transtheoretical Model of Behavior Change and Health Belief Model provided the theoretical basis for this study. Participants were health maintenance organization members aged 50 to 65 years (N=234). Using a cross-sectional, descriptive research design, data were collected using a mailed survey. Internal consistency (Cronbach's α=.96) and construct validity of the 13-item instrument were demonstrated. This unidimensional scale shows promise as a valid and reliable instrument to measure colonoscopy-related embarrassment and to inform development of interventions to reduce embarrassment, leading to higher colonoscopy completion rates and lower mortality.