Eye movement desensitization and reprocessing therapy (EMDR) has increasingly been proposed as an effective therapeutic procedure for post-traumatic stress disorder and other mental health problems. However, views on EMDR in the research literature have been polarized. Reasons for this are explored as is the nature and theoretical basis of EMDR. Fifteen controlled studies thus far published on EMDR and PTSD are reviewed, and it is concluded that (i) EMDR is an effective psychotherapy, (ii) EMDR's relative efficacy in comparison to behavioural exposure therapies has yet to be established, (iii) the role of eye movements and laterality in attentional focus remains controversial and (iv) a direct link between the theoretical basis of the therapy and observable psychological and neurobiological changes has yet to be established. Copyright © 1999 John Wiley & Sons, Ltd.