The Mannheim Carotid Intima-Media Thickness (IMT) Consensus (2004–2006) provides standardized guidelines for measuring and interpreting carotid IMT and atherosclerotic plaque. IMT, measured by ultrasound, is used as a surrogate endpoint in clinical trials to assess the effectiveness of interventions that reduce atherosclerosis risk factors. The consensus emphasizes the need for standardized methods to distinguish early atherosclerotic plaque from IMT thickening and to ensure consistent data collection and analysis across studies. IMT is defined as a double-line pattern on ultrasound images of the common carotid artery (CCA), formed by the intima-lumen and media-adventitia interfaces. Plaque is defined as a focal structure encroaching into the arterial lumen by at least 0.5 mm or 50% of the surrounding IMT, or a thickness >1.5 mm. These definitions help classify most carotid lesions observed with ultrasound. The consensus recommends specific ultrasound techniques for IMT measurement, including using linear transducers at frequencies >7 MHz, optimal depth and gain settings, and measuring IMT on the far wall for accuracy. It also emphasizes the importance of standardized protocols for image acquisition, analysis, and data interpretation to ensure consistency across studies. The consensus highlights the need for detailed data collection and analysis to reduce multiple testing issues and improve the reliability of IMT as a risk marker. While IMT is correlated with cardiovascular risk factors, it is not yet accepted as a formal risk factor. The consensus also addresses the importance of quality control, training, and certification of ultrasound centers and sonographers to ensure accurate measurements. In clinical trials, IMT and plaque measurements should be included as secondary endpoints, with careful consideration of the optimal primary outcome based on study design. The consensus underscores the need for further research to evaluate the predictive value of IMT in reducing vascular events and to determine its role as a surrogate endpoint in clinical trials.The Mannheim Carotid Intima-Media Thickness (IMT) Consensus (2004–2006) provides standardized guidelines for measuring and interpreting carotid IMT and atherosclerotic plaque. IMT, measured by ultrasound, is used as a surrogate endpoint in clinical trials to assess the effectiveness of interventions that reduce atherosclerosis risk factors. The consensus emphasizes the need for standardized methods to distinguish early atherosclerotic plaque from IMT thickening and to ensure consistent data collection and analysis across studies. IMT is defined as a double-line pattern on ultrasound images of the common carotid artery (CCA), formed by the intima-lumen and media-adventitia interfaces. Plaque is defined as a focal structure encroaching into the arterial lumen by at least 0.5 mm or 50% of the surrounding IMT, or a thickness >1.5 mm. These definitions help classify most carotid lesions observed with ultrasound. The consensus recommends specific ultrasound techniques for IMT measurement, including using linear transducers at frequencies >7 MHz, optimal depth and gain settings, and measuring IMT on the far wall for accuracy. It also emphasizes the importance of standardized protocols for image acquisition, analysis, and data interpretation to ensure consistency across studies. The consensus highlights the need for detailed data collection and analysis to reduce multiple testing issues and improve the reliability of IMT as a risk marker. While IMT is correlated with cardiovascular risk factors, it is not yet accepted as a formal risk factor. The consensus also addresses the importance of quality control, training, and certification of ultrasound centers and sonographers to ensure accurate measurements. In clinical trials, IMT and plaque measurements should be included as secondary endpoints, with careful consideration of the optimal primary outcome based on study design. The consensus underscores the need for further research to evaluate the predictive value of IMT in reducing vascular events and to determine its role as a surrogate endpoint in clinical trials.