Background: This article presents the psychometric evaluation of the Child-Adolescent Teasing Scale (CATS), an instrument to be used as a screening measure with middle school students. Methods: A 70-item scale was initially derived from qualitative data obtained from focus groups comprised of middle school students. A diverse sample of participants (N = 764) then completed the CATS and the Piers-Harris Children's Self-Concept Scale (PHCSCS); their mothers completed the Pediatric Symptom Checklist (PSC) and a demographic information form. A psychometric sample (N = 666) without missing data was used for subsequent analyses. Results: Principal components analysis resulted in a 32-item, 4-factor solution: "Personality & Behavior Teasing" (14 items), "Family & Environment Teasing" (7 items), "School-Related Teasing" (9 items), and "Teasing About My Body" (2 items). The standardized Cronbach's alpha for the final version was 0.94 and ranged from 0.83 to 0.90 for the subscales. The CATS's content validity, initially ascertained a priori by experts, was re-reviewed upon the instrument's refinement and supported. One-tailed t tests of mean differences between low- and high-scoring CATS groups on the PSC (t=-3.41, p less than 0.03) and the PHCSCS (t=-11.39, p less than 0.001) and supported the CATS's criterion-related validity. Conclusions: The 4-factor, 32-item CATS is psychometrically defensible and has demonstrated potential as a screening measure to identify students who are at risk from distressing teasing. (Contains 1 figure and 3 tables.)