The assessment of attachment in adolescence remains problematic, with the most widely used measure, the Inventory of Parent and Peer Attachment (IPPA; Armsden & Greenberg, 1987), argued to have major short-comings. This article reports two studies examining the psychometric properties of a shortened and modified version of the Experiences in Close Relationships — Revised (ECR-R) (Fraley, Waller, & Brennan, 2000), the Experiences in Close Relationships — Revised — General Short Form (ECR-R-GSF), for the assessment of general relationship attachment anxiety and avoidance in adolescents and young adults. Confirmatory factor analyses in two independent samples of high school and university students (Total N = 1187, 11 to 22 years) demonstrate support for the two-factor model of attachment anxiety and avoidance. The measurement model was supported across data sets and was not significantly different with respect to either age or sex. While the ECR-R-GSF demonstrated appropriate convergent and discriminant validity with the Relationships Questionnaire (RQ (Bartholomew & Horowitz, 1991) it did not converge with specific, parental relationship attachment as assessed by the IPPA. The ECR-R-GSF is argued to be a reliable and psychometrically sound instrument for assessing general attachment dimensions across a wide age range.