Working memory and attention are closely related concepts. Capture of visual attention by working memory (WM) contents has generated much interest in recent years. However, there is a lack of literature related to the time course of this attentional bias. In this dissertation I argue for a differential time course of WM driven attentional capture, for basic features and semantically related LTM contents, based on differences in activational pathways. Three experiments were designed to test these assumptions. Participants memorized a prime, for a later memory task. After a variable stimulus onset asynchrony (SOA), they then saw a search display for a target decision task. One of the items in the search display could contain a distractor item, related or unrelated to the WM content. In Experiment 1 primes and distractors consisted of basic features, colors and shapes. Experiment 2 investigated semantic and color primes in a single paradigm, using country names, with associated capitals and flags. Experiment 3 investigated primes semantically related to stylized objects. In support of the hypotheses, I found evidence that basic features held in WM attract visual attention rapidly, at very short intervals, while stimuli semantically related to WM contents develop attentional bias only at longer intervals. Additionally I found support for an inhibitory mechanism, leading to attentional allocation away from task irrelevant distractors associated with WM contents. The results support the differential time course of attentional effects of WM contents, based on type of stimuli, and highlight the importance of time course analysis when studying these effects.