Neural oscillations in the alpha frequency band (8-12 Hz) are among the most salient and ubiquitous phenomena observed in human electroencephalographic recordings. There have been various proposals regarding the functional significance of these oscillations, including the inhibition of task-irrelevant cortical areas, and the active retention of information in visual working memory. In an attempt to delineate between these two alternatives, I recorded EEG while participants performed two tasks requiring the short-term retention of visual working memory items. The results suggest that alpha-band oscillations reflect the implementation of an attentionally selective executive control process, inhibiting task-irrelevant processing, aiding the stability of active retention.