Self-report measures of adult attachment are typically scored in ways (eg, averaging or summing items) that can lead to erroneous inferences about important theoretical issues, such as the degree of continuity in attachment security and the differential stability of insecure attachment patterns. To determine whether existing attachment scales suffer from scaling problems, the authors conducted an item response theory (IRT) analysis of 4 commonly used self-report inventories: Experiences in Close Relationships scales (KA Brennan, CL Clark, & PR Shaver, 1998), Adult Attachment Scales (NL Collins & SJ Read, 1990), Relationship Styles Questionnaire (DW Griffin & K. Bartholomew, 1994) and J. Simpson's (1990) attachment scales. Data from 1,085 individuals were analyzed using F. Samejima's (1969) graded response model. The authors' findings indicate that commonly used attachment scales can be improved in a number of important ways. Accordingly, the authors show how IRT techniques can be used to develop new attachment scales with desirable psychometric properties.(PsycInfo Database Record (c) 2023 APA, all rights reserved)