The aim of the current study was to evaluate the psychometric properties of a recently developed measure of working memory: the Double Span Task. The Double Span Task is the first experimental task designed to assess all three components of Baddeley's (1992) model of working memory. The reliability of the Double Span Task was assessed in a sample of 105 older adults (M age = 64.3 yr., SD = 6.4). The internal consistency and test-retest reliability of the Double Span Task were good. The validity of the Double Span Task was assessed using a different sample of 49 older adults (M age = 70.0 yr., SD = 9.3). Performance on the Double Span Task was positively correlated with performance on a well-established measure of working memory, the Letter Number Sequencing Task. The Double Span Task also showed good discriminant validity. The Double Span Task is a reliable and valid measure of all three components of the working memory system.