The C-OAR-SE procedure, proposed by John R. Rossiter, is a new method for developing scales to measure marketing constructs. It stands for Construct definition, Object classification, Attribute classification, Rater identification, Scale formation, and Enumeration and reporting. The procedure is grounded in content validity, established through expert agreement after pre-interviews with target raters. Key steps include defining constructs in terms of Object, Attribute, and Rater Entity, and classifying these elements to determine the type of scale (single-item vs. multiple-item) and the precision of scores. The Rater Entity type significantly influences reliability. The article also discusses the limitations of traditional scale development methods, such as factor analysis and internal consistency reliability, and emphasizes the importance of content validity and logical arguments in the C-OAR-SE procedure. Examples and detailed explanations of each step are provided, along with a glossary of terms.The C-OAR-SE procedure, proposed by John R. Rossiter, is a new method for developing scales to measure marketing constructs. It stands for Construct definition, Object classification, Attribute classification, Rater identification, Scale formation, and Enumeration and reporting. The procedure is grounded in content validity, established through expert agreement after pre-interviews with target raters. Key steps include defining constructs in terms of Object, Attribute, and Rater Entity, and classifying these elements to determine the type of scale (single-item vs. multiple-item) and the precision of scores. The Rater Entity type significantly influences reliability. The article also discusses the limitations of traditional scale development methods, such as factor analysis and internal consistency reliability, and emphasizes the importance of content validity and logical arguments in the C-OAR-SE procedure. Examples and detailed explanations of each step are provided, along with a glossary of terms.