Abstract. We compared the psychometric properties of the American and Spanish versions of the Experiences in Close Relationship measure (ECR; Brennan, Clark, & Shaver, 1998 ; ECR-S, Alonso-Arbiol, Balluerka, & Shaver, 2007 ; Alonso-Arbiol, Shaver, & Yárnoz, 2002) , which assesses individual differences in attachment-related anxiety and avoidance. The American version of the questionnaire was administered to 1,265 Americans and the Spanish version to 747 Spaniards, all of them university students. The results indicate that the two linguistic versions are comparable, and that the Avoidance and Anxiety scales exhibit high internal consistency reliability in both languages, although the α values are slightly lower for the Spanish version. Avoidance was related to relationship status in both language groups, with about the same effect size. The factor structure of the measure was similar across both the American and Spanish samples.