While initially subject to debate, meta-analyses have shown that eye movement desensitization and reprocessing (EMDR) is effective in the treatment of posttraumatic stress disorder (PTSD). Earlier studies showed that eye movements during retrieval of emotional memories reduce their vividness and emotionality, which may be due to both tasks competing for limited working memory (WM) resources. This study examined whether another secondary task that taxes WM has beneficial effects, and whether the stronger the taxing, the stronger the reductions in vividness/adversity. A reaction time (RT) paradigm showed that counting backwards requires WM resources, and that more complex counting is more demanding than simple counting. Relative to a retrieval-only condition, counting during retrieval of emotional memories reduced vividness and emotionality during later recall of these memories. However, the counting conditions did not differ in the magnitude of this reduction, and did not show the predicted dose-response relationship. Implications for a working-memory explanation of EMDR and for clinical practice are discussed. Copyright © 2010 John Wiley & Sons, Ltd.