Since its first description by Charcot, psychological stress has been considered a triggering factor for exacerbations in multiple sclerosis, but until recently the clinical evidence for a causal relation was weak. Over the past years, a growing number of studies have started to elucidate this association and highlight potential mechanisms, including brain-immune communication. On 5 June 2005, a panel of international researchers discussed the current evidence. This article summarizes the observational, animal experimental, as well as human experimental findings on stress regulation in MS, as well as studies on the functioning of the major stress response systems, ie, the hypothalamo-pituitary-adrenal (HPA) axis and the autonomous nervous system (ANS) in MS. Consensus statements from the group to these aspects are given. Research objectives and strategies are delineated, as well as clinical implications.