Working memory allows individuals to maintain information in the focus of the mind's eye in the service of goal-directed behavior. Current psychological theories (for example, Baddeley's influential model of working memory) , computational models  and neurobiological accounts of working memory are based on the assumption that working memory operates on consciously represented information. Models of the capacity limits of working memory  are silent on this issue. While there has been some suggestion that working memory may be engaged by incidental exposure to visible items , current understanding indicates that the encoding of information in working memory, maintenance, retrieval and use in decision making of working memory operate on the contents of consciousness. But no study to date has investigated working memory processing for unconscious information. Here we show that observers can encode a subliminal orientation cue, maintain it 'on-line' even in the presence of visible distracters, and perform above chance in subsequent explicit discrimination, namely, whether a supraliminal orientation probe was tilted clockwise or counter-clockwise relative to the earlier unconscious cue. Our findings challenge the currently held view that working memory processes are contingent on conscious awareness.