This study examined the contribution of individual differences in rate of forgetting to variation in working memory performance in children. One hundred and twelve children (mean age 9 years 4 months) completed 2 tasks designed to measure forgetting, as well as measures of working memory, processing efficiency, and short-term storage ability. Individual differences in forgetting rate accounted for unique variance in working memory performance over and above variance explained by measures of processing efficiency and storage ability. In addition, the nature of the variation in forgetting was more consistent with a nonexecutive forgetting parameter than an executive ability associated with resistance to interference. These findings indicate that individual differences in the rate at which information is lost from memory is an important constraint on children's working memory performance, which has implications for current models of working memory that do not incorporate such a factor.